Over at the Carpundit's blog, he discusses why police departments don't buy foreign cars, and links to an article at CNN.com. One reason he points to and I agree with is that Government agencies, such as police forces usually buy American products, simply to "buy American." And of course discusses that until recently no foreign manufacturer produced a modle suitable to the job. Size and dependability are major reasons. Others involve cost and ease of repair.
In one sentence the Carpundit, who is a former lawman, wishes for all wheel drive for police cruisers. Here's the answer for many police forces, the 500 from Ford. Large enough, and available with all wheel drive. With the exception of the all wheel drive system, costs for repair and upkeep shouldn't be much more than the old Crown Vics or Caprices.