i found my import documents, and turns out i did pay the 6.1% tariff duty.
here's two other sites which confirm the exemption for 25 year old vehicles:
Hidden Taxes and Fees on Imported U.S. Automobiles
Welcome to the National Association of Automobile Clubs of Canada
looks like the cdn govt owes me a $1000 refund
i'll find out the official 'chapter and verse' for the exemption, and the refund process, and report back.
edit/update: "The authorities for the removal of the duty on 25 year old vehicles and their parts are Statutory Concessions 2440 (vehicles) and 2441 (parts) found in Schedule 2 of the Customs Tariff 1994."
from here:
http://www.bcsportbikes.com/forum/archive/index.php/t-83688.html