Actually, I think they are putting it on all A319/A320.
<font face="Verdana, Arial, Helvetica, sans-serif" size="2">
Air Canada is further demonstrating its support for the United States by applying a four foot square Canada/US flag decals to its Airbus A-319 and A-320 aircraft. The duo-flag decals are being applied to 76 aircraft as a visible sign of support and solidarity for the United States, the airline's largest market outside of Canada.</font>