The only concern that Canada Customs will have is whether you intend to leave either one of the vehicles (the truck or the moto) in Canada.

You haven't said what you plan to do with the truck once you load the moto onto the plane, so, I presume you plan to drive the truck back to the USA before you fly your body to Europe. If this is the case, when you enter Canada, you might want to have some paperwork (some correspondence with the shipping company) that indicates your intent to ship the moto out of Canada by air. I think if you show that documentation to the customs people and advise them that you plan to then turn around and drive the truck back into the USA, you should be fine.

Be aware, though, that once the motorcycle arrives at the airport in Europe, warehouse charges (storage charges) are typically about $100 a day, this because the storage charges are based on the cubic volume of the moto. So, you don't want to leave the moto sitting unclaimed at an airport in Europe for any longer than a day at the most.

Don't rule out other airlines operating out of Montreal, such as Air Transat. I've shipped with Air Transat a couple of times, and been very satisfied with them.

Shipping out of Canada will certainly be easier than shipping out of the USA, simply because there is less fear, uncertainty, & doubt associated with airports and airplanes in Canada than there is in the USA.

You will need to obtain "green card" insurance for the motorcycle, before you and it arrive in Europe, this so you can legally ride it in Europe. It might be prudent for you to get an IDP (International Driver Permit), which is basically a translation of your home driver licence that shows you are legally permitted to ride a motorcycle.

Finally, be sure you arrive at the Montreal airport with less than 1/4 of a tank of gas in the moto.

Here's a link to a post I made decades ago about how the paperwork process goes when shipping 'Dangerous Goods' by air (a motorcycle, being a flammable liquid-powered vehicle, is considered to be a DG): Rules for shipping motorcycles by air freight.

As I suggested in my first response to your question, spend a few hours studying what has been posted in the "Trip Transport" and "Trip Paperwork" sections of this forum, and you will find everything you need to know.

Michael