Not sure about the full legal picture but I do know our OC recently passed new by-laws allowing common property to be videoed and recorded. I don't know exactly why they did that but clearly they felt they had to formalise a situation that was already in place.
Here is what I think the general situation is:
If you are planning to record video images of common property, possibly to use in legal action of some sort, you have to put up signs warning people they are being filmed.
You may not, however, record audio without the person you're recording's clear permission.
And, bizarrely, you shouldn't put up signs saying you are video-taping common property when you're not (this stems from a case where a woman was raped in a lift that only had dummy cameras).
I hasten to add that this is just bits and pieces I have picked up. If anyone has a clear and concise guide to what can and can't be done (no endless quotes from incomprehensible laws and regulations, please), then let's have 'em. I don't mind being proved wrong as long as we get to the plain and simple facts.