It's an interesting scenario. And as more businesses mandate taking the vaccine, it's something we may end up finding out. At the end of the day, I think we let things play out and see where it goes.
I hope these are questions that whoever is in charge of this is trying to work out. Because realistically the majority of people are going to comply with whatever. And the minority of people who refuse to comply or are unvaccinated will not use the system, and in terms of how the passport works...
So more or less it will be like the ticketing guys on GO trains - come around, tap your Presto card (or scan a code in this case), and get a yea or nay.
And like with the ticketing guys on GO trains, anyone who gets a nay will likely raise a fuss.