Yes, but that downloaded map data is useless. You cannot search in it, find any routes in it or anything. You have to use the net and query Google. So it's more caching of the view than actual map data.
Not only that, but every now and then Google Maps want to check something over the Internet and just locks itself with an undismissable spinner and "Loading" message until you find a connection.
Well, it is seems like caching of the actual map data, but the application itself is not capable of performing the searches or figuring out routes. Since the device I am talking about was really not that powerful enough to perform that kind of computation, it could be intentional.