I found the filter hook woocommerce_disable_admin_bar
inside the file /plugins/woocommerce/includes/wp-customer-functions.php
.
Adding the following plugin in your site should do it:
(untested)
<?php
/**
* Plugin Name: (WooCommerce) Admin Bar for All
* Plugin URI: http://stackoverflow.com/a/22725557/1287812
* Author: brasofilo
*/
add_action( 'plugins_loaded', function()
{
add_filter( 'woocommerce_disable_admin_bar', '__return_false' );
});
/* Alternative (maybe add it inside 'plugins_loaded' hook) */
// remove_filter( 'show_admin_bar', 'wc_disable_admin_bar', 10 );