How to remove a parent theme template from Quick Edit?

Answer remade. The original was a wild idea…

The solution is the same as the one posted by Rarst in the question linked
How to *remove* a parent theme page template from a child theme?

Difference being the admin_head hook.
And a check for only running in edit-page and not in edit-post or edit-custom_post_type, as all these cases are fired by admin_head-edit.php.

The parent is “Twenty Eleven” and the child is called “Twenty Twelve”.

add_action('admin_head-edit.php','wpse_54054_remove_template');

function wpse_54054_remove_template() 
{   
    global $wp_themes,$current_screen;

    if('edit-page' != $current_screen->id)
        return;

    get_themes();

    $templates = &$wp_themes['Twenty Twelve']['Template Files'];

    $template1 = trailingslashit( TEMPLATEPATH ).'showcase.php';
    $template2 = trailingslashit( TEMPLATEPATH ).'sidebar-page.php';

    $key1 = array_search($template1, $templates);
    $key2 = array_search($template2, $templates);

    unset( $templates[$key1], $templates[$key2] );
}