It's not completely clear cut.
There's laws in the US about switching the place of manufacture to avoid tariffs that airbus/bombardier will have to circumnavigate but im sure if some journos know about this their lawyers will have scoped it out already.
This is a win win, bombardier gets to have a jet in the market, support from a big player and airbus gets to let someone else take all the risk to bring a product to market and then acquire a stake for very little risk in what has the potential to be a very very successful aircraft, once it's proven that its in demand and operating well.
The sticking it to Boeing bit will just be the cherry on top.