Add Custom PHP Page or File with Friendly URL

I created page template to display all the categories used on my wordpress blog. To display this file (as I’m sure you all know) I need to create a page in wordpress and use the template I created (even though the content in the WP interface is blank).

That has worked fine, but now I want to copy that template file to all the other blogs on our companies network. So my question is, is there a way to create a php file and give it a friendly URL so I do not have to go to each blog and create a WP page to use the template? I just want to upload the PHP file and assign it a friendly url.

This seems like an easy thing to do but I can’t find any information on it. Also, I am running the new WP MultiSite.