Very interesting!

Could be that the mysterious video van is on some kind of contract for mobile surveillance, on the look out for people involved in this incident?

I am familiar with various facial recognition software through my work and know that there are reasonable applications out there which can do very rapid matching. TfL uses these on some of the travelators in the underground. My guess is that the back of the van, the part with the mesh grating, is full of some kind of image processing machine.

This might make more sense with the "Working in partnership with the police" panel on the side. Some huge proportion of robberies and crimes occur close to the criminal's home. It might make sense for the police to monitor passerbys at peak times near the transport interchanges to see if they get a hit.