There are a few "get even" avenues that can be explored:

1) Increase landing fees at Canadian airports for US airlines flying Boeing aircraft by 300% thus making them less competitive and less profitable.
2) Do not purchase the interim F-18s from Boeing.
3) Do not purchase the Boeing's P-8 Poseidon to replace the old Aurora CP-140s.
3) Purchase Dassault's Rafale fighter jet instead of the Lockheed F-35s. Apparently Dassault would allow the Rafale to be assembled and maintained in Canada.  This would more than replace any work lost in Winnipeg if Boeing pulls out its manufacturing from Canada.
4) Partner with Comac, the Chinese aircraft manufacturer, to bring the CS500 to market.  The plane has been designed.  It could be flying in two years.  With Chinese labour costs and a compliant domestic market, Boeing's 737 (it's cash cow and most profitable aircraft) could get wiped out in China which is an even larger market than the USA.