We have the policy that you are to answer your city paid for cell 24/7. I blithely ignore this though. They've gotten used to me not answering and have stopped trying until the next Monday. If it's REALLY important, several top management know my home number, or at least know people that DO know my home number, so if the building catches on fire on a Saturday, I'll find out quick enough. I'm lucky enough to be expert enough on our systems that nobody else can do what I do, especially as quickly, so it's one of those cases where I do as I please, and they don't hassle me about it too much.