Excellent idea to document the value of our cars in the U.S. deal - just remember to convert to miles first! My initial calculation had a $2k mileage deduction before I realized this.
Buyback for my 2013 Golf with 80,000 kms (50,000 miles) is $21,557 U.S. or $28,412 Canadian. That's almost exactly double what the dealership offered me for a trade-in a few months ago.
Realistically, even if they do offer a buyback and even if they do convert to CAD (unlikely), it would make more sense to use the exchange rate from when I bought the car, which was closer to par - not sure how they would work that though to produce tables like in the U.S. deal. Maybe use an average conversion for each year.