In the case of my favorite hotel for which I have stayed a couple hundred nights, 100 in the last 3 years, I know the employees well and they commonly tell me when they are at 100%, as they do everybody when you check in and the aren't able to upgrade you. It is less common, but they also tell their weekday occupancy rates (it's a resort) when it naturally fits into a conversation. Like talking with an employee and saying, "Boy this place is dead compared to last weekend". A typical response would be, "Yeah we're only at 40% tonight, but Thursday we jump back up to 80% due to the XYZ conference and/or ABC event, and then we'll be back to 100% for the weekend". The Spa personnel will commonly tell me when it is going to get busy or slow so I can book my appointments accordingly.

It is proprietary information, but knowing the occupancy rate for a few days out of the year is not going to jeopardize the hotel's business. Trust me if the competition wants to know that information, there are a lot easier ways to do it than paying to stay at a competitor's hotel and trying to weasel some information from employees. No one is giving away any secrets the competition isn't already aware of in some form or fashion.