Doesn't work with Fios, bummer.
You can watch recorded shows on your DVR on FiOS, no? I have FiOS, but haven't really ever had the urge to watch it on my phone...but I seem to recall the option. Can you DVR the game, and watch it as it's recording? I'm not sure if there would be any issues of lag or image quality...but if you're watching on a tablet, I think the lag is probably irrelevant, and the image quality isn't that awful.
I assume the lack of NESN Go on FiOS is an authentication issue. It seems silly of them not to fix that, although I do see a lot of Xfinity/Comcast/NBC stuff at the Garden, and I do have a choice between FiOS and Xfinity. This doesn't tip me at all, but it might tip some...