i used to work @ cartech (before enfield auto auctions went broke) where all nsw police vehicles were put together and all mods done to them.
theyre nothing special, just a xr8 with the so called "chip" installed. the "chip" is just another computer circuit board installed in them to wire up all the radars,terminals and other bullshit they have to run.
main problem they had was that with all the digital recording equipment they started using the cars were overloading and shitting themselves mid pursuits, which led them to install big arse capacitors to hold power in them during the chase.
drove a few cop cars through the yard and around the carpark area, when they came back to be stripped and sold as stock standard cars, they werent worth much anymore.