Actually... I was searching for some help on this subject and found your post in my search. I can help answer this and I also need some help.
Yes, it does work. I started playing AlphaJax and you will get game invites and notifications of turns with numbers... as you should expect.
That said, however, and to the point of my question... anyone playing alphajax have you noticed that your notifications never go away? In the notification portion of the Game Hub, I still have squares saying "MY TURN" and "GAME INVITE". When I tap them they take me to the game I just played or finished. They never go away.