Apart Plod doing there own bodges to the Fuse Box wiring for there own Aux Equipment, the only thing Ive found between Plod Saloons and normal is a 'Boot Release Mod' which is additional wiring and additional Boot Relay Mod Kit, allowing the Boot to be released with Ing Key in on Early's and Instant Boot release without waiting counting the seconds on the Late ones.
I always thought the above was a Hardware only Mod, but could have also been Software assisted or related via a Tech 2.

I had a London DPG a few years back that totally throw me come MOT time, as the rear Fogs wouldn't work and the wiring was interrupted and went to this Boot Mod Relay via the Fuse Panel, which meant you had to switch on the rear Fog Switch (Fogs Lights were wired to a separate Flasher) and hit the Boot Release Button at the same time to open the Boot. At the time was kind of thinking maybe this was a added Security feature for the Gun Cabinet in the Boot, but on reflection now my thoughts are The rear Fogs were not wired correctly when being put back as standard and leaving the Force.