Yep, Gatsobait, they're the ones who wanted to introduce the fart tax, though when examined it wasn't quite as stupid as many of their other policies - it's all relative though.
The cops theoretically must give a 10% leeway, and all fixed and mobile cameras have at least a 10% leeway built in. Having experimented with a number of fixed cameras on my motorbike (no number-plate on the front

), the majority (all mounted in 50km/h zones) don't seem to fire until 65km/h or so.
However, enforcement is worse. As Samco rightly states, all jam sandwiches have forward and backward pointing radar systems with instant-on capability. Radar detectors are legal and widely used, but not much protection against a radar sysem that can turn on and get a valid lock withing .5 of a second or so.
After a significant number of complaints recently, the Police have severely curtailed their use of unmarked cop cars (they might be unmarked, but they're ALL late model Holden Commodores or Ford Falcons and you can spot the radar units and cop radio aerials from a mile off anyway). However, most highway speed traps are carried out on the few spots where it is possible to get some speed up and overtake. Running speed traps on overtaking lanes is commonplace depsite having been identified by the coroner's court in one instance for causing an accident.
All camera vans are unmarked Toyota Hiace models with a rear-mounted camera inside the vehicle. Instead of using an infra-red flash, it uses an orange flash-gun when operating at night. As the camera points towards the oncoming traffic, having it go off at you on a dark night is really clever. Destroys your night vision and temporarily blinds you. I've been tempted, should I ever set one off in a car, run into the side of the camera van and sue the cops for wilfully blinding me. Could be an expensive exercise though...
One of the other main issues is inappropriate speed limits. I personally feel that 100km/h is simply too low, despite even the main trunk roads being single carriageway. Arterial routes within major cities (Auckland, mainly) are universally 50km/h. Very very rarely is a road set higher than that, and only when it's a multi-lane divided road with houses or businesses that are set well-back from the road or on side feeder roads. One particular road in Auckland, Tamaki Drive, is aboue a mile and a half long. Two lanes in each direction (not divided) and has just TWO driveways, one of which protected by traffic lights, along its entire length. 50km/h the whole way.