Well as someone who painfully had to cancel due to Tesla giving me no choice (pick up the vehicle today or cancel). I would love to be given a second chance.
I wish you the best but it likely won't happen. If a court rules in favour of Tesla it will likely entice the government to simply change the rules again but be inclusive of Tesla. This is the path of least resistance. It's possible that the pressure from a court case would be bad optics for the Ontario PC and they may quietly settle and just make the adjustment and move on.
Unfortunately that would likely mean no recourse if you've cancelled. They are not going to create a convoluted set of rules for people who have cancelled and now want the car. This is just my opinion.