While i'm fully aware my rental can often have GPS tracking etc for the rental company, I have never, ever seen a rental with a camera filming the occupants, and I've rented a lot of cars around the world. I cant find any evidence of this online either.

The one example I can find where a lens was present in the cabin from Hertz appears to be part of a navigation system feature that was never used, and Hertz even then had to handle public backlash for the disabled camera. The public backlash/reputation damage of filming private occupants in the cabin solely for the security benefit of the rental agency would be pretty significant too, to the extent I can't imagine this happening in most Western nations.