From the Fedex site:
"What is FedEx International MailService?
How it Works
We pickup your international mail and move it to a regional mail center where we tender it to a foreign postal authority for delivery to the mail recipient. Tell me more about how it works.
What you can send
Send marketing materials, brochures, postcards, letters, catalogs, invoices, and general customer communications. You can also send low value merchandise such as DVD, CDs, samples, books, audio tapes, diskettes, videotapes."
Sounds like it is just using the mail, with a little extra bit of a fee.
Apparently it can include proof of delivery.
I would guess that you would be just as likely to have Canada Post charge you their fee for "brokerage" as for any other parcel.
And by the way, used goods are just as subject to duty and taxes as new ones.