The stationary cameras operate from sensors in the road, called "piezo electronic detectors." You trip the first sensor by driving over it, then as you cross the second sensor the computer brain thingo calculates your real time speed. Too fast, and "FLASH!" And no, travelling really closely behind someone won't save you...Have a walk past a speed camera location and you will see the sensors embedded in the roadway.
HWP won't target a location already monitored by cameras. They wouldn't run the risk of having a driver cop two fines for the same offence on exactly the same location. They often run traps with a "chase car," so one unit can shoot the speed and the other goes after the offending motorist. The 2nd HWP car is often hidden from immediate view. Think Mona Vale Road as an example of this. Another reason for running multiple cars is if they were using the ANPR system, catching unregistered or stolen cars, as well as unlicenced/suspended/disqualified drivers.
As an aside, radar/lidar operates differently to the static cameras, allowing Police to "shoot" your speed from hundreds of metres away.
djc, there is a speed camera on King Georges Road, between Stoney Creek Road and Edgbaston Road. Is this the one you mean, near the primary school? If so, it will be focussing on the location outside the school, as it is a variable speed limit camera. There is also a red light camera at the intersection of King Georges Road and Stoney Creek Road. There is a safety camera at King Georges Rd and Moorefields Rd, but that's up the road at Roselands. All the camera sites are listed on the RTA website, even though I believe they shouldn't list them at all...
Everyone should be travelling at the limit or just under it anyway, so camera locations shouldn't need to be spoon fed to those drivers who can't keep to the limit. The good Lord gave us trackdays for a reason... I have no dramas with HWP running speed traps for the drivers who slow down for cameras (usually to 10km/h under the limit, very annoying) and then speed up again (back over the limit, also annoying). Stupid enough to get caught = stupid enough to have to deal with the consequences. And yes, I've been caught once before by a camera. And this business of warning everyone where HWP are working at...that's just strange. Personally, I don't have much time for people who are keen on helping others avoid punishment for breaking the law. But that's just me...
*Prepares to be flamed like a fire at a gas bottle factory...*