Adding multisite taxonomy support to custom post types.

tagging_topics_post_types.php

<?php
add_filter( 'hsph_plugin_tagging_topics_post_types', 'cchange_register_cpt_for_tagging' );
add_filter( 'hsph_plugin_tagging_cchange_issues_post_types', 'cchange_register_cpt_for_tagging' );
add_filter( 'hsph_plugin_tagging_cchange_subtopics_post_types', 'cchange_register_cpt_for_tagging' );

function cchange_register_cpt_for_tagging( $post_types = array() ) {
	// Array of custom post types.
	$cutom_post_types = array( 'cchange_article', 'cchange_issue', 'cchange_subtopic', 'cchange_bio', 'cchange_class', 'cchange_event' );
	// Merging default post types and custom post types.
	$post_types = array_merge( $post_types, $cutom_post_types );
	
  return $post_types;
}