There are Amex lounges and there are Amex express lines (the same as first class and frequent flyers) to get through security, but there are NO special Amex check in lines.
Air Canada treats it's Super Elite like platinum. You have Super Elite, you will always get upgraded if there is room. However, having an Amex Black card does not get you an upgrade. It just means you can afford to pay Exec class. Airlines do not upgrade you because of your credit card (unless you are using it to pay for the upgrade). Why the heck would they? THIS IS A MYTH THAT SOME FOLKS HERE ARE PERPETUATING.
You might be right. I have no knowledge of Air Canada's relationship to Amex. That is why I did not mention AC.
I do know you get free top tier status and their status cards with specific airlines and/or hotels with some credit cards. Even a lowly peon like I get popped up to top tier with the right credit card. Mind you I am only platinum with one chain, and with the Centurion card you get it on several. Why? Well most Centurion travellers are already Emerald / Super Elite / etc fliers. And they are not the type to book lower costs seats and risk not being upgraded. So there is a huge effort made to get them it try first class seats on any airlines company's metal. Also why would they fly on an airline that did not treat you as a "super-elite" passenger?
Perhaps the confusion exists because the ticket agents do not see the Amex card. I have a credit card. Because I have that brand / level of card I get the top tier card for a hotel chain. When a reservation is made using my information the hotel knows I am a top tier VIP type guest. The probably assume I stay in their hotels a lot. But it is all about my having their VIP card. The card is provided to me because of my tiny little credit card.
I do know that at least in MIA, LHR, NYC, JFK, and HKG if you book through the free concierge service for Centurion card holders you are met by a greeter who walks you through the check in. Not exactly a "special check in line" but why quibble? They come and find you. (I know it was true about 10 years ago, I have not flown with a centurion Card holder since then Applies to the card holder and those travelling with them. I was only a hanger on. But it was nice to see how your CEO travels.
By the way.... back to the Amex / Air Canada links.... Even for a standard Platinum Amex card their web site tells us.....:
1 Bypass the regular check-in line at the airport with access to Air Canada Executive First®*/Executive Class®* Priority Airport Check-in
2 Avoid the line-ups at security by accessing the Pearson Priority Security Lane
3 Breeze through airports lines with Air Canada Executive First®**/ Executive Class®** Priority Check-in
Not bad when you realise the card only requires a $40, 000 a year income and ok credit to get. Not the quarter million spend for the Black Card.
So.... I know that any empty 'better' seats are offered to the Super Elite travellers, then the Elite, etc etc. (ya some ticket type rules apply. I know). I elect to assume my CEO was not lying when he said he was given the super elite and Emerald status by airlines as a perk for having his Centurion card.

. So perhaps you can accept my much shorter statement that you get automatic upgrades
Of course you may be right.
