It should be easy to port over to iphone since I believe this is being made in unity. Only thing is you have to fork over for the iphone version of unity :( Been learning Unity and man seems simple then gets hard :(
Usually it's used for lightmaps (example on Unity, or from polycount wiki, also on Unreal [1] [2]) . Talking about Unity, note that I'm not sure about that, maybe the detail maps are using UV2? (if a Unity user can confirm)