Has been used to criminal effect in a couple of films... in one a woman is targeted by an unsavoury character who decides to shut down her Saab 9-7X (Cadillac SRX/Buick Rainier) in the pouring rain late at night, using the OnStar system... Another obvious example is in Die Hard 4.0, when the geek and Brucie nick that 5 Series
obviously that was a bit daft as had the operator looked at the Map she would have seen that the car was, in fact, in Washington DC rather than some quiet country back road
but the principle is sound.
Given that the technology is in place and in use, the Police don't actually need direct access to the systems, merely contact with the relevant control centre together with a reliable link to the Department of Very Lazy Antagonists to cross reference registrations with chassis numbers, all done in a Police control room somewhere rather than in car. Once confirmed, a quick call to BMW assist, or Volvo etc could see the car shut down, provided it is factory fitted with an 'On Call' system. Arguably this system could be fitted without the purchaser of the vehicle knowing, regardless of the options ticked, assuming of course that this isn't already the case
The DMV in the States is much more effective at processing this information given the far more local way that the US is organised. There the officer types the reg into his computer, and up comes everything, whereas here, they generally have to call in for a VIN check