Forge maps are not made assembled inside of Maya.
They make the assets inside of maya and import them into their engine as tags. then they assemble them inside of another app called Guerilla.
I'm not exactly sure of their current system but it most likely has not changed from what I just described to a completely Maya driven pipeline for a number of reasons, not the least of which is half of the artists using other tools, 3ds max/XSI/modo.
They have had Guerilla and tags since Halo 1 and I don't think they will go and rewrite their whole system just for Halo 4.
That doesn't mean they couldn't make something like what your saying, but its highly unlikely given their audience, platform and diminishing returns.
I don't mean to shrug off your post since I'm sure some folks didn't know, but I thought my joke was pretty obvious :lol sorry