This is a little plugin that adds the event name to the page's <title> tag. Requires Event Espresso 3.1.35.P or higher.

espresso-custom-title-tag.php

<?php
/*
Plugin Name: Custom Espresso Title tags
Plugin URI: http://gist.github.com/
Description: Adds the event name to the page's <title> tag. Requires Event Espresso 3.1.35.P or higher.
Version: 1.0
Author: Josh Feck
License: GPLv2
*/

/**
 * Creates a nicely formatted and more specific title element text
 * for output in head of document, based on current event.
 *
 */
function ee_reg_page_title( $title, $sep ) {

	// only do stuff if espresso_get_event exists
	if ( function_exists('espresso_get_event') ) {
		global $this_event_id;

		if (isset($this_event_id) && !empty($this_event_id)){
			$event_id = $this_event_id;
		}
		
		if ( empty( $event_id ) ) return $title ; //get out this isn't an ee page.
		
		$event = espresso_get_event( $event_id );

		//one more sanity check
		if ( empty( $event ) ) return $title; //get out we don't have an event.

		if ( $event_id ) { // if there's an event id...do stuff...
			$event = espresso_get_event( $event_id );

			$title = '';
	
			// Add the site name.
			 
			$title .= get_bloginfo( 'name' );	
      
			// Add the event name.
      
			$title = "$event->event_name $sep $title";
	
			return $title;

		}
	}
}

add_action( 'action_hook_espresso_social_display_buttons', 'ee_mod_page_title');

function ee_mod_page_title() {
	add_filter( 'wp_title', 'ee_reg_page_title', 10, 2 );
}