The whole locker room thing isn't like you might think. They already have verbiage to keep anatomical boys out of [actual] girls' locker rooms, and vice-versa. Just like in already-co-ed sports.
Look up this dude named Falon Fox. Got his thingy cut off and was beating the piss out of females in MMA fights in less than two years and never told his first opponents she used to have a penis.