Some experience from the '96 Atlanta Olympics-the police beat, spray, kick and then arrest. Then after the Olypmic park bombing, they got really tough. If you looked wierd, you got hauled away. For a couple of years before the Olympics the police roughed up and encouraged troublemakers to leave. None of this went on the books, because they wanted the crime numbers to look lower.
You can expect to be beaten, charges with false charges, and your bikes are toast.