Correct me if I'm wrong, but Blackhouse isn't a gym, it's a management company. A lot of these fighters train out of different gyms.
You're partially right. They also have their own gyms now.
Lyoto Machida, former UFC LHW hamp
Future UFC MW Champ
Benavidez, Barao, Aldo, Nate, Nick, Lyoto, TBD, JDS
Forever hanging in Anderson Silva nuts