I used to have one on my old scooby back in the UK but it was a pain in the arse updating it all the flipping time with the new fixed GATSO's and time distance cameras for motorway road works. So haven't bothered over here and yes the NZP do use the radar guns having seen them a handful of times on SH1 and 2.
The unmarked cars that the police use stick out like a sore thumb to me, meaning where they are parked,how they are parked then number of ariels attached and the not so covert lights installed in each corner of the rear window. All you have to do is just keep your vision up as far as you cane see and as already mentioned don't draw attention to yourself by driving like a TWAT......!!
I do the same a mentioned by a few people already cruise around 110 and touch wood never had any problems but when your driving a two and a half ton defender 110 is about max speed anyway....lol lol