> If true then turning off the circuit breaker would probably default every single one of them to locked.

Maybe, but that's super against fire code. Locks on doors in environments like these need to fail safe, not fail secure. Otherwise the building catches fire and loses power, and all the doors lock everyone inside to burn to death.

And also a super easy thing to fix for any locksmith that isn't totally useless. You can just rewire the door's circuit so there's no power to the strike. No power = no magnetism = unlocked door.