I think Air Canada's definition of a "true" hub is an airport that serves unique long haul destinations that are not served from other cities in their network. YYZ, YUL and YVR each serve long haul routes that are exclusive to those airports.
eg. for an Air Canada pax to reach Seoul on AC metal, they must connect thru YVR. To get to Brussells one must go thru YUL, and to fly to Rio YYZ. YYC does not serve any such long haul route exclusively, and likely never will. So while we are a strong connector for our local region, we are do not fit their true definition of a "hub". Just my interpretation, I could be wrong. Interested to hear what others think.
With the exception of the United States, and maybe now China, very few, if any, countries would be able to support an airline with 4 or more hubs. Even 3 is a stretch. It becomes very difficult geographically and economically to do so. And I would argue that were AC based out of Toronto, even YUL would not enjoy the true hub status that it does now.
Interesting to note they give a special mention to YYC on page 38, calling Air Canada a "Strong #2 in Calgary". I thought AC had more flights/day than WS, but maybe they are basing it on available seats? Either way, I sure wish I had bought some AC stock back in December of 2011
By my definition, I guess that makes YHZ and YYT "true hubs" for Westjet..but I'll save that discussion for a later day.