I like to keep my berserkers injured so they get the damage and speed bonus.
So I unpowered my Medical Bay and saved the game. When reloading the game, it was powered again.
I suspect this is done due to the fix of a previous old issue when freshly repaired buildings remained unpowered by default. I would change that fix so the automated power on is applied to all the facilities in the base only when a building repair finishes.