These are 'guidelines'. They can put them wherever they want. ACA/TT do stories on this every few months.I think if you look into the rules a speed camera cannot be placed within 500m of a speed change or a hill. Though Victoria maybe different as its filled with money grubbing scum.
Oh as well as that a statistic was released a few years ago with the amount of accidents caused my speed cameras EG: Braking due to camera, looking at speed camera and verging into oncoming traffic etc.