Is court testimony based on them then, legal? It's possible that such recordings might be used (until some lawyer challenges it, anyway)

As far as I know, yes.

I did a quick web search, and didn't find any news to it being every challenged. (found a couple Canadian articles decrying it).

Again, since this is a public issue, I don't think they can be.

Maybe we can ask LAM,E for an opinion. :)

watch hoods and masks become commonplace fashion statements. Not everyone is comfortable with the police watching everything you do, with the only respite being to hide on private property.

And the West thinks the Arabs are old-fashioned and archaic. :)

As to the police powers - the seizure law is so obscene as to be worthy of question how it ever was passed.