I used to live in Manchester above a busy junction.
It seems the Prison vans are typically the exception to the rule, every week at rush hour (I assume after the courts were done for the day) you would get a police escorted prison van heading to Strangeways, and wow do those guys not **** around!
This is the layout, they are turning left at the red light
I assume they can't take chances for high profile cases by being stuck in traffic but the police motorcyclists would often routinely go up alongside a car at a left turn traffic light and tell them to go through the red light and pull over, the bikes would then go through, block the traffic and the vans and police escort would go through.
You would often see people being told to mount the pavements and when people sat at the red lights unsure whether to go through or not, more often than not a smack to the window and vigorous gesticulating by the police motorcyclist would get them moving.