The police are subject to the same laws as the rest of us. That said, if they have to junp a light in order to do their job, then they will,knowing that they are still accountable if there is a collision.
If a plod on a blue light run gets camerad, he's in the clear provided it's not excessive, justified by circumstances, etc. If not on an emergency run then he can see a ticket or a disciplinary hearing.
I think the MTB police are great, there are a few in Leeds. They are very effective at silently and quickly patrolling housing estates where there are kerbs, grassy areas and so on. The spotty youths doing deals on street corners are less enamoured.