Saw a piece on a proggie some time ago so details/memory are sketchy but
> one thing I definitely remember is that they have twice as much
> servicing, ie, if a particular cars service schedule is every 9k,
> police do them every 4.5k.
If you read that schedule carefully you'll probably find the servicing requirements are different for arduous use. And Mr Plod ain't going to wait for the engine to warm properly if on a shout. Etc.
Other thing I'm willing to bet is they don't use the approved oil on their BMWs etc - just a good general purpose one for all their vehicles.