Canada does not have debtor’s jail. Nothing will really happen except that more fines will keep racking up. No collection agency is going to take on a homeless person’s debt, so eventually those debts will just disappear, assuming he makes no effort to pay them off.
In the meantime, if he tries to escape homelessness, it’s a lot harder nowadays to find an apartment with a landlord that doesn’t check your credit, and 100k+ in unpaid debts looks really bad.