A WordPress page template to identify what page templates are being used where.

page-template-usage.php

<?php
/*
Template Name: Page Template Usage
Description: A page template to identify what page templates are being used where. BRAAAM
*/

get_header();

// Array of page template name => template filename
$templates = array(
	'Template Filename' => 'template-filename.php',
);

echo print_page_links_by_template( $templates );

get_footer();

/**
 * Returns array of post objects where the specified $template is used.
 *
 * @param   string  $template  The template file name.
 * @param   array   $args      Array of additional args accepted by get_pages.
 *
 * @return  array              Array of post objects matching the query.
 */
function get_pages_by_template( $template = '', $args = array() ) {
	if ( empty( $template ) ) {
		return false;
	}

	if ( strpos( $template, '.php' ) !== ( strlen( $template ) - 4 ) ) {
		$template .= '.php';
	}

	$args['hierarchical'] = 0;
	$args['meta_key']     = '_wp_page_template';
	$args['meta_value']   = $template;
	$pages                = get_pages( $args );

	return $pages;
}

/**
 * Returns links to the pages by the template used.
 *
 * @param   array  $templates  Array of templates.
 *
 * @return  string             HTML markup of Template Name and pages where used with edit link.
 */
function print_page_links_by_template( $templates ) {
	$page_list = '';
	if ( $templates ) {
		foreach ( $templates as $template_name => $template_file ) {
			$page_list .= '<h3>' . $template_name . ' - ' . $template_file . '</h3>';
			$pages = get_pages_by_template( $template_file );
			if ( $pages ) {
				foreach ( $pages as $page ) {
					$page_list .= '<a href="' . get_permalink( $page->ID ) . '">' . $page->post_title . '</a> <a href="' . admin_url( 'post.php?post=' ) . $page->ID . '&action=edit" style="font-size: 85%;">(Edit)</a><br />';
				}
			}
		}
	}

	return $page_list;
}