Surveillance does deter minor offenders and first time offenders. It absolutely helps women with minor incidents like gropings and other intimidating behavior.

But ultimately major incidents won't be affected. Usually this is why buildings need to be locked up. It's likely that anyone willing to commit a major offense in that scenario is not someone attached to the building itself. Anyone within a company can be easily traced, they'd also be aware of the surveillance.

I think the idea this does nothing is ignorant, deterance is a major factor for the most frequent incidents.