In my town's public library they have cameras in the bathroom. However they claim they cant see into the stalls or the urinals, and that they are only used in review after a claim or incident, and are never archived longer than 48 hours when the system overwrites the old recording.
It all depends on the local laws. City, county, state, and federal can have all different things in there and it can be very confusing, when in doubt go with the most local law.
I personally would go into the empty restroom with some friends and start doing an interpretive dance show for the person viewing it on the other side... If it isn't a camera you at least have some practise time in. =)