Remember that NBC doesn't put on this event, they just have the broadcast rights to it. The musical acts are entirely outside their control (though I'm sure they could help pull strings to get, I don't know, America's Got Talent performers...)
I didn't see the whole show (just this video), but it looks to me like WMAQ's involvement is to provide the hosts and most of the broadcast aspect (the boring camera shots give away that someone who directs news for a living is directing the video here). The audio feed of everything happening on the stage is probably a mix from the "house board" (if they were using a system like Dante they could potentially have a "house mix" and an "air mix" on two separate boards, but I doubt it) more than likely being operated by someone from the audio vendor, which is why the hosts are so loud in comparison.
WMAQ's involvement with the actual event itself is just about the same as the vendors who supplied the lights, trussing, staging, etc.