In BC we have the Vehicle Sales Authority of BC and Ontario has the same kind of thing.
Look in the FAQ's here:
https://www.omvic.on.ca/portal/Consu...oIndustry.aspx
and there is actually a link to this question (Lien on a car traded in that the dealer agreed to pay)... if there is no timely resolution, you can make a claim to the Motor Vehicle Dealers Compensation Fund.
I forgot to mention that the OMVIC should cover all 'registered' dealerships in Ontario, it doesn't matter if it's a BMW (or any major brand) dealer or a smaller private one.
Good luck!