The Police, like all other emergency service drivers are not exempt from the law. In the event of an accident, they are subject to much higher levels of scrutiny than the public, I can attest to this having been at the receiving end of a Notice of Intended Prosecution following an RTC while driving an Ambulance.
If you watch any of the "in car documentaries" where the police are in pursuit of a vehicle, you are more likely to see the passenger providing the commentary, you will see the Ambulance attendant using the radio and you will see the fire service supervisor on a fire tender use the radio, not the driver. If a Police traffic car is single manned then they often have a PTT switch allowing messages to be sent, personal radios are never hand held and many have in the ear headsets. Drivers do not engage in long conversations, messages are short and to the point.
If any of these drivers are in an accident, they face a real chance of prosecution. The view taken by the CPS is that as we all received a higher standard of driver training and that a higher standard is therefore expected on the road; if an accident happens, then this higher standard is used as the yardstick for prosecution. What would be seen as a case of careless driving and potentially a caution for any other road user, would be prosecuted as the higher offence of dangerous driving for an emergency services driver.
I will pose you a question. If your house is being burgled and the offender is still there and has a knife, or if you are trapped upstairs with your house on fire or you are in your living room and your child has choked on a peanut, do you want the emergency service driver to be worrying at every stage about whether their next move will have them ending up in court facing the loss of their job or do you trust them to drive to the best of their ability making the maximum progression to come and help you ?