When is the {$new_status}_{$post->post_type} transition hook fired?

It is fired in wp-includes/post.php on line 3026
in the following function:

wp-includes/post.php: line 3014-3027

function wp_transition_post_status($new_status, $old_status, $post) {
    do_action('transition_post_status', $new_status, $old_status, $post);
    do_action("{$old_status}_to_{$new_status}", $post);
    do_action("{$new_status}_{$post->post_type}", $post->ID, $post);
}