Clearly, hot air emission rights will come cheap. Similarly, international scofflaws might be willing to sell non-surplus emission rights at bargain basement prices. Buying these cheap emission rights may thus reduce the compliance costs for individual emitters. But we need to distinguish between what's in the best interest of an individual firm and what is the best interest of Canada as a whole. Because individual emitters are always those that reap the benefits of lower emissions focusing narrowly on the issue of reducing an individual emitters greenhouse gas reduction costs does not give the most economic solution.
Capital flows out of Canada.
This isn't a matter of comparative advantage because we are not getting anything for our money. Moreover, Canada doesn't get any of the benefits associated with reduced greenhouse gas emissions. If one accepts that a deal that is purportedly about protecting the environment should be used to prop up the Russian economy this might be persuasive. Under hot air trading, there would, indeed, be an infusion of capital into the former Soviet bloc. Under the Marshall Plan, the US government and the predecessor to the OECD ensured that money went to real reconstruction projects.