The answer is.... YES! They can. NO, they don't have to tell you. Some labor negotiations call for generic notification that cameras will/may be used. But they don't have to tell where. But, that is a labor agreement, not a law. The only place you are protected from video surveillance is where there is an expectation of privacy... like a bathroom. But, hold your weiners... there has been some case law that permits that as well if their is eveidence a crime is being committed. Then the only protection usually calls for m/m or f/f monitoring.
Any other place can be monitored at anytime even if there is no evidence a crime is taking place, or policy broken. Sorry, to ruin the thoughts on the jailhouse legal eagles who have posted bad advice in response to your question. In a nut shell, ask your Union rep if you work in a communist.... I mean union shop. If it is an open shop... it's their house, their rules (short of bathrooms and dressing rooms)