The relevant legislation is the “Workplace Surveillance Act 2005”.
Section 9 – This Part applies to the surveillance of an employee carried out or caused to be carried out by the employee’s employer while the employee is at work for the employer
I don’t believe that either knowing about a camera, or the lack of action to have a camera removed would qualify as having “caused” the surveillance to be carried out.
Section 10 (6) – Notice to an employee is not required under this section in the case of camera surveillance at a workplace of the employer that is not a usual workplace of the employee.
So even if you were worried that the OC had “caused” the surveillance, it does not include any trades that you have have on site (unless they are permanently there).
I drive on-site with a dash camera and I don’t think my employer would be in breach as it’s my personal dash cam. It would be different if they supplied the camera, though.
That’s my layperson’s opinion after reading the act.
From what I have seen where a supposedly qualified lawyer has commented on this sort of thing is that there is pretty much no right to privacy when in a public place, and even in private places there are only very specific and limited privacy rights.
Of course, if it’s attached to common property then there’s a whole avenue to get it removed (although for someone who is that way inclined, and who has already purchased the surveillance gear, it may end up being “moved” rather than “removed”).