Without a BMW insider to ram this repair thru the system you are at the end of the road.
You could roll the dice and try a bluff. You could send BMW Canada a formal letter of complaint indicating the issue. You would indicate if they fail to act you will commence a small claims court action. Of course you would be one of thousands who have threatened small claims court action in the last decade or two.
Then you would need to actually file the small claims court action after you determine which County to file it in and who exactly are the defendants.

Then you wait and see if you get a call. If not, prior to the hearing date you will need to withdraw. You might end up paying BMW $500. for costs.
You withdraw because your chance of success is ZERO. First there is the issue of this having a US warranty. Then of course who is your expert witness? Is he BMW certified and if so how long ago? How much is he gonna cost ya? BMW will send an automotive engineer or two who are expert in giving evidence.
Your entire claim centers on something that has yet to occur; that it may occur in the future. At best, the Judge would advise you to re file when the motor does blow up.
The most effective action is to use removable paint and plaster "LEMON" on the side of this Z car and park outside a Bimmer store. Believe me the dealer ppl will come out and speak with you and just might move this along.
Pics would be great.