I'm the author of Tabify Edit Screen ( http://wordpress.org/extend/plugins/tabify-edit-screen/ ). My plugin enables tabs in the edit screen and the user can manage them.
The problem now is that your plugin doesn't really has a method to call that it only add the meta boxes for a certain post type. Even all is not a problem. I would say that the way you add meta boxes is wrong and that it would be a better way to add them when the action add_meta_boxes is called.
My solution to make your plugin work in my plugin is the following code:
http://plugins.trac.wordpress.org/changeset/529615. I was wondering what your comment is about this code. It now runs for every post type.