“Brains Out” is now playable on Rock Band 3 for Xbox 360 and can be purchased either from the in-game music store, Live Marketplace on the 360 dashboard, or online from the following link :
http://marketplace.xbox.com/en-US/games/offers/80000e6b-0000-4000-8000-000045410914
Thanks to Redditor Vince Caccamo for hooking this up and That Authoring Group for transcribing it and putting us in the game!