Privacy is on a sliding scale. There are certain assumptions we rely on when we go out in public.
Imagine, for example, some future where you were effectively under constant surveillance when in "public". Where your every action, every movement, every utterance was recorded, categorized, transcribed, data mined, and then put into a feed that anyone could subscribe to. That's what the complete absence of public privacy looks like, and it's not great.
But, AIUI, those cameras aren't networked together. They're all owned by different people. TV shows like Torchwood that show some agency tracking someone across the city using CCTV are showing something that can't possibly happen in real life, because there is no one centralized authority (or even handful of authorities) that have access to most of those cameras. Not to mention the cameras themselves are just video, and not particularly stellar quality at that.
Of course, I could be wrong, maybe someone in London really can track someone across town using the CCTV cameras, but the above is what I understand from what other people have explained in the past.
