Yep, they are. They have been expanding their readers as well, to all lanes instead of just NEXUS.
Sort-of. They are passive, which means they only broadcast when they receive a signal, and they use the power from that signal to respond.
No. It's a very short read range, and it's not illegal to have someone else's card. It's a little odd, but as long as there is a valid explanation and no intent to use it fraudulantly, Canada doesn't have an issue with it.
If it's in a wallet or something, it's not going to get picked up. Antennas are 20+cm square, and only read from a few feet.