/\Actually apparently '86 was only a Recognized Exposition. The Universal Expositions are done only every 5 years now - (2000 Hannover, 2005 Nagoya/Aichi, 2010 Shanghai and 2015 Milan) while the smaller Recognized Expos are staged in between. A number of major World cities including NY, Manila and Sao Paulo have expressed interest in bidding for 2020 - so a Universal Expo is increasingly becoming an event that only very large cities can undertake, adn thus probably out of reach for Calgary or Edmonton. That's probably why relatively small, isolated Calgary lost to Nagoya for 2005, even though many considered Calgary to have the superior bid.
Anyways, I see nothing wrong with both cities throwing their hats in the ring to be Canada's official bid city. Bottom line is, Calgary and Edmonton are the only two Canadian bid cities so one way or another, Canada's Expo candidate will be in Alberta!
I think if Alberta were to land the Expo, it would be very good for either city. Even these smaller Recognized exhibitions typically draw over 10 million attendees - so this would be a major boon to either city, bringing potentially millions of tourists, much needed infrastructure dollars, and at least some measure of international attention.