POC - Can I include vocabularies from one Drupal site within another?

taxonomy_central.module

<?php

/**
 * The name of the taxonomy central database, usually from $databases
 * configuration in settings.php
 */
define('TAXONOMY_CENTRAL_DATABASE_NAME', 'vocabulary_server');

/**
 * Controller class for taxonomy central vocabularies.
 */
class TaxonomyCentralVocabularyController extends TaxonomyVocabularyController {
  public function load($ids = array(), $conditions = array()) {
    db_set_active(TAXONOMY_CENTRAL_DATABASE_NAME);
    $entities = parent::load($ids, $conditions);
    db_set_active();
    return $entities;
  }
}

/**
 * Implements hook_entity_info().
 */
function taxonomy_central_entity_info() {
  $info['taxonomy_central_vocabulary'] = array(
    'label' => t('Taxonomy central vocabulary'),
    'controller class' => 'TaxonomyCentralVocabularyController',
    'base table' => 'taxonomy_vocabulary',
    'entity keys' => array(
      'id' => 'vid',
      'label' => 'name',
    ),
    'fieldable' => FALSE,
  );

  return $info;
}

/**
 * Implements hook_menu().
 */
function taxonomy_central_menu() {
  $items['taxonomy-central'] = array(
    'title' => 'Taxonomy central',
    'page callback' => 'taxonomy_central_callback',
    'access arguments' => array('access content'),
    'type' => MENU_CALLBACK,
  );

  return $items;
}

function taxonomy_central_get_vocabularies() {
  return taxonomy_central_vocabulary_load_multiple(FALSE, array());
}

function taxonomy_central_vocabulary_load_multiple($vids = array(), $conditions = array()) {
  return entity_load('taxonomy_central_vocabulary', $vids, $conditions);
}

function taxonomy_central_callback() {
  var_dump(taxonomy_central_get_vocabularies()); die();
}