Just stumbled upon this on the AC site. I remember they had something like this about 4 years ago, and they were $40 each...

Rapidair Upgrade Certificates
Rapidair Upgrade Certificates are available in books of four at airports, city sales offices and travel agencies in Montreal, Ottawa, Toronto, Calgary, Edmonton and Vancouver. They are sold in booklets of four certificates for Cdn. $100, plus applicable taxes.

-Each certificate is valid for a one-way upgrade to Executive Class from full economy fares for one year from date of issue
-Valid on all Air Canada Rapidair routes
-Upgrades can only be applied to a previously-purchased ticket with confirmed reservations
-Upgrade reservations can only be made within 48 hours of departure
-For upgrades to be honoured, the certificate must be presented at check-in
-Upgrades are subject to availability and number of allowable upgrades per flight