Vehicle registration details are being captured. Only if the license plate of the vehicle you are driving is present on a vehicle of interest (VOI) database, will an alert be generated in the control room of the vetted company that subscribes to that particular camera.

Is surveillance footage considered to be in public or private space?

Surveillance footage is of public space, i.e. movement and vehicles. Most security companies use analytics software systems to identify unusual behaviour, which prevents operators from having to watch continuous footage and allows them to only concentrate on alerts of unusual behaviour.