Upgraded with a paper certificate had the word "CERT" on the BP (at least when you printed your own at OLCI) so it was easy to tell even if they failed to staple the certificate. Plus when they scanned the BP I'm pretty sure it flashed on their screen, at least at the gate it did.

Under the old system, at YVR domestic MLL, my experience was pretty consistent. I had to show my E card when seated in Y and when upgraded on a certificate. I did not have to show it when in paid J or when on a complimentary upgrade from a Latitude flight pass. This, from my reading, was in line with the published T&C.

Now, under eUpgrades, the relevant T&C read (emphasis added): "Although you will be seated in the Executive cabin when your upgrade is confirmed, your booking will remain subject to the fare rules and restrictions of the booking class you originally purchased. These rules include, but are not limited to, mileage accumulation, change and cancellation fees, access to airport lounges and baggage allowance."

Source: http://www.aircanada.com/en/aeroplan...grades/tc.html

Interestingly, last weekend at YUL domestic, the lounge agent told me that the only reason for asking for my E card is to give me wireless access. She said that's why the wireless access screen asks for your AE number, and if you are not swiped in to the lounge it does not help. As far as she's concerned, a J BP now means lounge access. Seems clear from the T&C that she is wrong. As usual when going to any lounge, YMMV.

Net result: unaccompanied P or non-status do not get lounge access even with a seat upgrade. And I would agree with yvr76, that is petty, especially considering the vanishingly small percentage of lounge entrants would be unaccompanied upgraded P/non-status. Perhaps that's why the lounge agents frequently don't enforce the rule.