Answer regarding 250g less are here in my post: Toronto Mavic Owner: where can I fly?
However, even though you can (as they are toys) you still have to be responsible. That means, if you are not responsible and cause any risk (even if its a toy) then your going to be legally responsible.
Id' also add... think about this - if your flying a drone, people around you do NOT know its 250g or less... get ready to talk to the cops as you will get people calling it in
