When we were shooting there around 3-5am, they didn't say a word to us. We even had our Queen of Hearts sitting ON TOP OF THE GRAND PIANO.
There was another really legit-looking photographer there, too, shooting the two Trinity Blood Queen Esthers, and they didn't say anything to either of our groups. I think as long as we're there at an empty time, they're cool with it! Also, looking less professional might help, too, hahaha. XD