One question (or maybe two):
does Unity runs inside the win8 VM, or the GameOS VM?
If it is in the GameOS VM, is it the same GameOS where usual games run into?
And last... I guess very obviously, it won't use MONO but rather support for scripting, right?
Unity itself would run on your PC where you'd compile it. You'd use the xbox version of SN-Target something to push it to the SDK which it would run I imagine in some sort of Debug OS state? I guess it's similar to the official game state, with a handful of possible debugging features.