plugin to auto-subscribe usergroup based on usergroup user is in

editflow-autosubscribe.php

<?php
/*
Plugin Name: Edit Flow - Auto Subscribe
*/

function efx_auto_subscribe_usergroup( $new_status, $old_status, $post ) {
    global $edit_flow;
 
    // When the post is first created, you might want to automatically set
    // all of the user's user groups as following the post
    if ( 'pending' == $new_status ) {
        // Get all of the user groups for this post_author
        $users_to_follow = get_users( array( 'role'=> 'editor', 'fields' => 'ID' ) );
        $edit_flow->notifications->save_post_following_users( $post->ID, $users_to_follow );
    }
 
    // Return true to send the email notification
    return $new_status;
}
add_filter( 'ef_notification_status_change', 'efx_auto_subscribe_usergroup', 10, 3 );