Don't spose you know any technical detail/spec about these cameras do you? You have listed which way you wil get done, eg: north, south etc, however when looking at these intersections, you can see on the road the the sensors for these cameras are on both sides.
Also led to believe, that at every light change, these things record 8 seconds of footage, from when the light changes from amber into red.
A bit of info on the camera units:
http://www.redflex.com/files/Red%20Fixed.pdf