If there is a video camera with audio hidden in a coat rack in the bathroom at work, is this legal?

No.  That is not appropriate.  You have a right to privacy.  There may also be peeping/sexual misconduct going on here.  You should really contact local law enforcement and talk to them about what is going on.  I would contact them at the station, after which they would come out to the work location and forward a report to the district attorney's office.

Best of luck.