Meta box that allows publishing a post to another site of the network

publish-to-network.php

<?php
/**
 * Plugin Name: Publish to Network 
 * Plugin URI:  https://gist.github.com/brasofilo/7036415
 * Description: Meta box that allows publishing a post to another site of the network
 * Version:     1.0
 * Author:      Rodolfo Buaiz
 * Author URI:  http://wordpress.stackexchange.com/users/12615/brasofilo
 * Text Domain: sepw
 * Domain Path: /languages
 * License:     GPLv2 or later
 */ 

/*
Publish to Network 
Copyright (C) 2013  Rodolfo Buaiz

This program is free software: you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation, either version 2 of the License, or
(at your option) any later version.

This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
GNU General Public License for more details.

You should have received a copy of the GNU General Public License
along with this program.  If not, see <http://www.gnu.org/licenses/>.
*/

add_action(
    'plugins_loaded',
	array ( B5F_Publish_To_Network::get_instance(), 'plugin_setup' )
);
 
class B5F_Publish_To_Network
{
	/**
	 * Plugin instance.
	 *
	 * @see get_instance()
	 * @type object
	 */
	protected static $instance = NULL;
 
    
	/**
	 * URL to this plugin's directory.
	 *
	 * @type string
	 */
	public $plugin_url = '';
 
    
	/**
	 * Path to this plugin's directory.
	 *
	 * @type string
	 */
	public $plugin_path = '';
 
    
	/**
	 * Meta data name.
	 *
	 * @type string
	 */
	private $plugin_meta = '_network_published';
 
    
	/**
	 * Constructor. Intentionally left empty and public.
	 *
	 * @see plugin_setup()
	 * @since 2012.09.12
	 */
	public function __construct() {}
 
    
	/**
	 * Access this plugin’s working instance
	 *
	 * @wp-hook plugins_loaded
	 * @since   2012.09.13
	 * @return  object of this class
	 */
	public static function get_instance()
	{
		NULL === self::$instance and self::$instance = new self;
 
		return self::$instance;
	}
 
    
	/**
	 * Used for regular plugin work.
	 *
	 * @wp-hook plugins_loaded
	 * @since   2012.09.10
	 * @return  void
	 */
	public function plugin_setup()
	{
		$this->plugin_url    = plugins_url( '/', __FILE__ );
		$this->plugin_path   = plugin_dir_path( __FILE__ );
		$this->load_language( 'plugin_unique_name' );
 
		if( is_multisite() )
		{
			add_action( 'save_post', array( $this, 'cross_publish' ), 10, 2 );
			add_action( 'add_meta_boxes_post', array( $this, 'add_custom_box' ) );
		} else
			add_action( 'after_plugin_row_publish-to-network/publish-to-network.php', array( $this, 'plugin_row' ) );
	}
 
    
    /**
     * Warning when activated on single sites
     */
	public function plugin_row()
	{
		echo '<tr class="plugin-update-tr"><td colspan="3" class="plugin-update colspanchange"><div class="update-message" style="font-size: 1.3em; color:#f00">This plugin only works in Multisite! And does nothing in single sites.</div></td></tr>';
	}

    
	/**
	 * Add meta boxes.
	 *
	 * @wp-hook add_meta_boxes_post
	 * @since   2013.09.09
	 * @return  void
	 */
	public function add_custom_box() 
	{
		global $post;
		$termid = get_post_meta( $post->ID, $this->plugin_meta, true );
		if( empty( $termid ) || 'none' == $termid )
		{
		    add_meta_box( 
		        'sectionid',
		        __( 'Post to other site of the network' ),
		        array( $this, 'inner_custom_box' ),
		        'post',
		        'side',
		        'high'
		    );
		}
		elseif( 'donotshow' != $termid )
		{
			$details = get_blog_details( $termid['bid'] );
			$site = sprintf(
				'<a href="%s" target="_blank" style="font-size:1.2em">%s</a>',
				$details->siteurl,
				$details->blogname
			);
		    add_meta_box( 
		        'sectionid',
		        __( 'Posted to: ' ) . $site,
		        array( $this, 'inner_posted_box' ),
		        'post',
		        'side',
		        'high'
		    );
		}
	}
	
    
	/**
	 * Meta box for publishing post
	 *
	 * @wp-hook add_meta_box
	 * @param   object $post
	 * @since   2013.09.09
	 * @return  void
	 */
	public function inner_custom_box( $post )
	{
	    $blogs = $this->get_blogs();
		echo '<select name="my_blog_id" id="my_blog_id">';	
		echo "<option value='0'>- Don't publish -</option>";
		foreach ( $blogs as $site ) 
		{
			if( get_current_blog_id() != $site->blog_id )
			{
				$details = get_blog_details( $site->blog_id );
				printf(
					'<option value="%s" title="%s">%s</option>',
					$site->blog_id,
					$site->domain,
					$details->blogname
				);
			}
		}	
		echo '</select>
		<div id="feedback" class="misc-pub-section"><small>Destination Site:</small><br><label for="my_blog_id">&nbsp;</label></div>';
		echo '<label><input type="checkbox" name="disable_cross_publish" /> Remove this box</label>';
	    wp_nonce_field( plugin_basename( __FILE__ ), 'B5F_Publish_To_Network' );
		$this->print_script();
	}
	
    
	/**
	 * Meta box for published posts
	 *
	 * @wp-hook add_meta_box
	 * @param   object $post
	 * @since   2013.09.09
	 * @return  void
	 */
	public function inner_posted_box( $post )
	{
		$termid = get_post_meta( $post->ID, $this->plugin_meta, true );
		if( !empty( $termid ) )
		{
			$details = get_blog_details( $termid['bid'] );
	        switch_to_blog( $termid['bid'] );
			$po = get_post( $termid['pid'] );
			$perma = get_edit_post_link( $termid['pid'] );
	        restore_current_blog();	
			printf(
				'<p><a href="%s" target="_blank">%s</a></p>',
				$perma,
				$po->post_title
			);
		}
	}
	
    
	/**
	 * jQuery for live Checkbox
	 *
	 * @since   2013.09.09
	 * @return  void
	 */
	private function print_script()
	{
		echo <<<HTML
<script type="text/javascript">
jQuery(document).ready( function($) 
{
	$('#feedback label').html( $('#my_blog_id').children("option:selected").attr('title') );

	$('#my_blog_id').live('change', function()
	{
		var site_domain = $(this).children("option:selected").attr('title');
		var site_name = $(this).children("option:selected").text();
		$('#feedback label').html(site_domain);
	});					
});    
</script>
HTML;
	
	}


	/**
	 * Save post action.
	 *
	 * @wp-hook save_post
	 * @param   integer $post_id
	 * @param   object $post_object
	 * @since   2013.09.09
	 * @return  void
	 */
	public function cross_publish( $post_id, $post_object )
	{
	    if( defined( 'DOING_AUTOSAVE' ) && DOING_AUTOSAVE )
	        return;

	    if( defined( 'DOING_AJAX' ) && DOING_AJAX )
	        return;

	    if ( !wp_verify_nonce( $_POST['B5F_Publish_To_Network'], plugin_basename( __FILE__ ) ) )
	        return;

	    # Block auto-drafts and revisions
	    if( in_array( $post_object->post_status, array( 'auto-draft', 'inherit' ) ) )
	        return;

	    $termid = get_post_meta( $post_id, $this->plugin_meta, true );

		if( isset( $_POST['disable_cross_publish'] ) )
		{
			update_post_meta( $post_id, $this->plugin_meta, 'donotshow' );
			return;
		}
		
	    # It's a new post
	    if( empty( $termid ) && isset( $_POST['my_blog_id'] ) )
	    {
			if( '0' == $_POST['my_blog_id'] )
			{
				update_post_meta( $post_id, $this->plugin_meta, 'none' );
				return;
			}
				
	        remove_action( 'save_post', array( $this, 'cross_publish' ) );
	        switch_to_blog( $_POST['my_blog_id'] );
	        $my_post = array(
	          'post_title'    => $post_object->post_title,
	          'post_content'  => $post_object->post_content,
	          'post_status'   => 'publish',
	          'post_author'   => $post_object->post_author,
	        );
	        $new_post = wp_insert_post( $my_post );
	        restore_current_blog();
	        add_action( 'save_post', array( $this, 'cross_publish' ), 10, 2 );
	        update_post_meta( 
				$post_id, 
				$this->plugin_meta, 
				array(
					'pid' => $new_post,
					'bid' => $_POST['my_blog_id']
				)
			);
	    }
	}

    
    /**
     * Get blogs list
     * 
     * @return array List of blog ids
     */
    private function get_blogs()
    {
        // get blog list from cache
        $blogs = get_site_transient( 'multisite_blog_list' );

        if ( FALSE === $blogs ) {

            global $wpdb;
            $blogs = $wpdb->get_results(
                $wpdb->prepare( "
                    SELECT blog_id, domain
                    FROM $wpdb->blogs
                    WHERE site_id = %d 
                    AND public = '1' 
                    AND archived = '0' 
                    AND mature = '0' 
                    AND spam = '0' 
                    AND deleted = '0' 
                    ORDER BY registered ASC
                ", $wpdb->siteid ) );
            // Set the Transient cache
            set_site_transient( 'multisite_blog_list', $blogs, 60*60 );  
        }
        return $blogs;
    }

    /**
	 * Loads translation file.
	 *
	 * Accessible to other classes to load different language files (admin and
	 * front-end for example).
	 *
	 * @wp-hook init
	 * @param   string $domain
	 * @since   2012.09.11
	 * @return  void
	 */
	public function load_language( $domain )
	{
		load_plugin_textdomain(
			$domain,
			FALSE,
			$this->plugin_path . 'languages'
		);
	}
}

Hi, I've a similar function already in use, but what I cannot retrieve on save_post is the taxonomy of current $post_id, so that it's possible to apply the same taxonomy (or create if not exists) in the second site..I see that you don't manage this, but maybe you know hot to do..?
thanks