Update: I got through to a supervisor with CP and went over the program details line by line. The 1kofferis open to all members of the Frequent Flier program. 300000 letters were sent out but only to draw attention to the program. In writing it states that you do not have to have a letter to qualify.

The codeshare issue is more murkey. The supervisor had to call headquarters and even there they did not come up with a total agreement. If you fly a codeshare ticketed by Canadian but not the metal(operated by Canadian), you could put yourself in jeapordy. To be safe you have to fly either a Canadian marketed and OPERATED AIRCRAFT!!!!
Candian regional does qualify. This is different from the American interpetation of the rules that state as long as it is ticketed by CP you are ok.

I hope this clears up any confussion.

If anyone was hoping to qualify on Canadian with a codeshare on Alaska/Horizon the only way to play it safe is to take a round-trip to Victoria from Vancouver on Canadian--very affordable and cheap insurrance for insuring getting a full 100k. There are probably many other Canadian Regional flights you can take but the Vancouver/Victoria option makes the most amount of sense for people flying up to Vancouver from Seattle.