Fanpage code is created on facebook's site, it not specific to Joomla. You just paste that code into a custom html module.
Let me be clear. I can put a site through an iframe Fanpage and controls it through a specific extension for joomla.
Here is an example of how this is possible and already exist on other platforms:http://premiumcoding.com/wordpress-facebook-page-themes/
This I say it would be cool to have in Vertex!