hook_menu not working with alias
That behavior is not inclued in core. You can try this two modules:


Sub-pathauto (Sub-path URL Aliases): The Drupal Path module matches only full URLs when creating SEO-friendly aliases. This module extends that behavior by also matching known sub-paths and replacing them with their respective alias.
Extended Path Aliases: SImilar to previous module, but includes more functionlaity. The drawback is that it needs core patching (adding a line to nclude/path.inc) or installing PECL runkit library.