95% of Police cars are not chipped with anything other than what is supplied by Holden or Ford or Mitsubishi or any other brand they may use.
The other 5%, who knows.
Certainly nobody working for Holden or servicing standard police cars would know what was in or done to the cars that are serviced in house, and yes they do exist.
The average Police Pack has the standard chip with the possible slight mods to the idle as mentioned previously. Because the Holden specs show it was delivered that way does not mean it stays that way after delivery. Holden would have no idea.
On the other hand it doesn't prove that some are fitted with aftermarket chips either.
Unless you are currently in the Force and servicing these cars I don't think you could say with conviction one way or the other if chips are fitted to some vehicles.
The only Police cars that I can say are certainly modded and running performance chips, among other things, is the old Tango 1 and new Tango 1 drag cars here in Perth. They were prepared by the Police Force.
The only true answer to the original question is that no ex cop car is sold with anything but the standard chip so if you do buy one with an aftermarket chip someone else put it there.