No duty or processing fees charged. And that makes sense. Under NAFTA, it is the country of origin of goods that determines duty. The tickets are printed in the US and are only usable in the US. No duty on that!
The worst duty is usually charged on clothing that is made overseas and shipped from the US. Big mail order companies like Lands End or LL Bean will collect the duty and save you the processing fees, but smaller companies just ship it across, and UPS has to charge the duty due and adds a brokerage fee on top. I'm careful to check the country of origin for most stuff we mail order from the US.