From USA to Europe via YYZ on AC:

http://www.aircanada.com/en/travelin...z_us_intl.html

From Europe to USA via YYZ on AC:

http://www.aircanada.com/en/travelin...z_intl_us.html

No, nothing like the backward US CBP procedures to have to collect bags, clear custom and re-check-in nonsense.