Police RV on Nostrand and Park

Has anyone noticed how the police RV, which was slightly south of Atlantic, randomly appeared off of Nostrand and Park this week? Yesterday evening and this afternoon a massive amount of cop cars showed up and parked next to it. Now here is the odd thing the cars are from the 77th, 75th, 79th precincts as well as FSD. What's going on? Crime suppression? Response to some major criminal activity?

It appears that they do shift change detail at the RV. Don't know why. There haven't been any major crimes or incidents on that corner in months. 

And it was gone by noon today.