WordPress taxonomy trail in slug

custom-post-type.php

// Post type 'expertise'
add_action( 'init', 'create_expertise_post_type', 4 );
function create_expertise_post_type()
{
  	$labels = array(
		'name' => __( 'Expertise' ),
		'singular_name' => __( 'Expertise' ),
		'add_new' => __( 'Add New' ),
		'add_new_item' => __( 'Create New' ),
		'edit' => __( 'Edit' ),
		'edit_item' => __( 'Edit' ),
		'new_item' => __( 'New' ),
		'view' => __( 'View' ),
		'view_item' => __( 'View' ),
		'search_items' => __( 'Search' ),
		'not_found' => __( 'Not found' ),
		'not_found_in_trash' => __( 'Nothing found in trash' ),
		'parent' => __( 'Parent' ),
	  );

	$args = array(
		'labels' => $labels,
		'description' => __( 'This is where you can create a new Item.' ),
		'public' => true,
		'show_ui' => true,
		'capability_type' => 'post',
		'publicly_queryable' => true,
		'exclude_from_search' => false,
		'menu_position' => 4,
		'hierarchical' => true,
		'_builtin' => false, // It's a custom post type, not built in!
		'rewrite' => array( 'slug' => 'expertise/%expertise_type%', 'with_front' => true ),
		'query_var' => true,
		'supports' => array( 'title', 'editor', 'author', 'thumbnail', 'excerpt' ),
		'taxonomies' => array('expertise_type'),
	  );

	register_post_type('expertise',$args);
}

custom-taxonomy.php

add_action( 'init', 'create_expertise_type_taxonomies', 0 );

function create_expertise_type_taxonomies()
{
  // Add new taxonomy, make it hierarchical => true for categories-like taxonomies)
  $labels = array(
    'name' => _x( 'Expertise', 'taxonomy general name' ),
    'singular_name' => _x( 'Expertise', 'taxonomy singular name' ),
    'search_items' =>  __( 'Search Expertise' ),
    'all_items' => __( 'All Expertises' ),
    'parent_item' => __( 'Parent Expertise' ),
    'parent_item_colon' => __( 'Parent Expertise:' ),
    'edit_item' => __( 'Edit Expertise' ),
    'update_item' => __( 'Update Expertise' ),
    'add_new_item' => __( 'Add New Expertise' ),
    'new_item_name' => __( 'New Expertise' ),
    'menu_name' => __( 'Expertise' ),
  );

  register_taxonomy('expertise_type',array('expertise'), array(
    'hierarchical' => true,
    'labels' => $labels,
    'show_ui' => true,
    'query_var' => true,
    'rewrite' => array('hierarchical' => true),
  ));
}

functions.php

add_filter('rewrite_rules_array', 'mmp_rewrite_rules');
function mmp_rewrite_rules($rules) {
    $newRules  = array();
    $newRules['expertise/(.+)/(.+)/(.+)/(.+)/(.+)/?$'] = 'index.php?expertise=$matches[5]'; // use the 5th tax segment
    $newRules['expertise/(.+)/(.+)/(.+)/(.+)/?$'] = 'index.php?expertise=$matches[4]'; // use the 4th tax segment
    $newRules['expertise/(.+)/(.+)/(.+)/?$'] = 'index.php?expertise=$matches[3]'; // use the 3rd tax segment
    $newRules['expertise/(.+)/(.+)/?$'] = 'index.php?expertise=$matches[2]'; // use the 2nd tax segment
    $newRules['expertise/(.+)/(.+)/?$'] = 'index.php?expertise_type=$matches[2]';
    $newRules['expertise/(.+)/?$'] = 'index.php?expertise_type=$matches[1]';
    return array_merge($newRules, $rules);
}

function filter_post_type_link($link, $post)
{
    if ($post->post_type != 'expertise')
        return $link;
    if ($cats = get_the_terms($post->ID, 'expertise_type'))
    {
        $link = str_replace('%expertise_type%', get_taxonomy_parents(array_pop($cats)->term_id, 'expertise_type', false, '/', true), $link); // see custom function defined below
    }
    return $link;
}
add_filter('post_type_link', 'filter_post_type_link', 10, 2);

// my own function to do what get_category_parents does for other taxonomies
function get_taxonomy_parents($id, $taxonomy, $link = false, $separator = '/', $nicename = false, $visited = array()) {
    $chain = '';
    $parent = &get_term($id, $taxonomy);

    if (is_wp_error($parent)) {
        return $parent;
    }

    if ($nicename)
        $name = $parent -> slug;
else
        $name = $parent -> name;

    if ($parent -> parent && ($parent -> parent != $parent -> term_id) && !in_array($parent -> parent, $visited)) {
        $visited[] = $parent -> parent;
        $chain .= get_taxonomy_parents($parent -> parent, $taxonomy, $link, $separator, $nicename, $visited);

    }

    if ($link) {
        // nothing, can't get this working :(
    } else
        $chain .= $name . $separator;
    return $chain;
}