Default taxonomy template in plugin, override in theme

This is what I ended up using (for all those interested):

    function override_tax_template($template){
        // is a specific custom taxonomy being shown?
        $taxonomy_array = array('tax1','tax2');
        foreach ($taxonomy_array as $taxonomy_single) {
            if ( is_tax($taxonomy_single) ) {
                if(file_exists(trailingslashit(get_stylesheet_directory()) . 'tax-template-directory/taxonomy-'.$taxonomy_single.'.php')) {
                    $template = trailingslashit(get_stylesheet_directory()) . 'tax-template-directory/taxonomy-'.$taxonomy_single.'.php';
                }
                else {
                    $template = BASE_PLUGIN_DIR . 'includes/tax-template-directory/taxonomy-'.$taxonomy_single.'.php';
                }
                break;
            }
        }
        return $template;
    }
    add_filter('template_include','override_tax_template');

I hooked into template_include to check if there was a file in the active template called taxonomy-YOUR-TAXONOMY-NAME.php and if not, loads the default from your plugin.