As I understand it the US is not using the provisions of NAFTA to settle Boeing's complaint. Instead the US trade department will impose duties as it did with softwood lumber (which, by the way, is not covered by NAFTA).

The US lumber lobby wants to restrict access of our wood to US markets. Boeing's intentions fall into the same category and their arguments are just as spurious. As of today the big losers of the US lumber lobby are US consumers. 

I would not be surprised if Delta agrees to pay the tariffs just so they can get the C Series aircraft. Boeing must be running scared.

Based on this I think the author of this article is somewhat out to lunch. He makes some fair points but they are irrelevant.