I read that they are part of the Safe-T-Cam camera systems. From: https://www.speedcameras.sa.gov.au/about_speed_and_red_light_cameras, "Safe-T-Cam cameras are on major arterial roads and detect heavy vehicle driver fatigue and all unregistered vehicles". It does appear that they perform registration checks on all vehicles. I couldn't find any enforcement for registration on the wiki so I tagged it as enforcement=registration. The fatigue checks is less descriptive but I read online it is able to check how long a hsv has been driving for and if it exceeds a certain amount of time they get fined. Again, I couldn't really find an enforcement value that is a maximum driving time so I marked as speed_camera (but importantly only for HSV vehicles). I also can't find a generic traffic camera node on the OSM wiki that isn't speed_camera. If there is a better way of marking them feel free to update it.