there is no restriction on taking (not indecent) photos of other people (in public places)

Quite right, though I heard it as (yes) public places, but litigation appertained to the reproduction thereof. So unless you print or broadcast there would be no case. Witness the ubiquitous pixelation on videos, these days. I would bet there were lawyers willing to posit the concept of digital images seen on the camera's screen as reproduction. Depending who sees them, I guess.

Images taken in private places need permission beforehand - in theory.

Then there are laws regarding security cameras, they must be overt and point away from other peoples' windows, from my understanding.