Should it be of interest, The Gatso 36 Type Approval was updated in 2008 to include speed detection (see below)
The red light detection is done via in-road sensors before and after the stop line. I think the speed is detected via road sensors and confirmed via a photo taken when the vehicle is over some road markers placed further down the road. Such a detection system would be vulnerable to sharp braking - if applied in time.
But that could be said about the offence of speeding generally...
