Technically, yes, you must have an award booked on an Air Canada flight, to get all those extra benefits (priority check-in, free first baggage, priority boarding, MLL), but you might as well try and gain access at the lounge anyways. Just give them your boarding pass and CIBC Visa card, and see what the system says after your card is swiped. To be blunt, it's such a screwed up new 'feature' that you may get access.

As for the coverage on Aeroplan redemption flights, most people aren't aware that only the CIBC and TD Aeroplan Visa cards will provide flight coverage when used to pay the award's taxes and fees. There are a couple of threads here on Flyertalk that discuss this. No Amex card, not even their Aeroplan Plus Gold/Plat cards, will offer this coverage. But to find out you'd best call your card provider to clarify. Several of us did call Amex to get the awful truth, no coverage on Aeroplan awards. In reality though, several people have reported that their Amex cards did give them the coverage, but YMMV.

Here's one thread discussion:
http://www.flyertalk.com/forum/american-express-membership-rewards/1520470-amex-canada-travel-insurance-questions-consolidated-3.html#post22737378