By their advance preparation (pole cam, on scene in advance), the police demonstrate having advance notice that THIS DAY and THIS PLACE was going to be hot. They knew the Cossacks were planning to "crash the meeting."
So, what did they do? They waited in their cars, just out of sight, and made sure that none of their people were inside the restaurant. They avoided confrontation, until it was too late.
I do understand that instigation and awareness are not the same thing, and my suspicion is that the cops played both parts, although I wrote here mostly of the awareness angle.
Setting up a 'kill zone'(cross-fire) is more than an awareness.
It implies more than awareness, it implies premeditation .
The existance of an ariel camera reinforces the concept of premeditation , and planning , not just a happenstance situation.
The delay and reluctance in releasing information even more furthers the inuendo that there is something that it actively being hidden.
On the date of the event, police attempted to enter the restaurant, but were blocked by management. State and local authorities then occupied positions outside the restaurant, including on the rooftop of a neighboring restaurant, Don Carlos.