How about hit the owners of the trucks with the largest legally possible parking fine + storage fees. If they deny responsibility (say it was a driver doing crazy shit, not company policy), offer to wave all the fees, in exchange for a statement that anyone operating their vehicle at this protest had no permission to use that vehicle for that purpose and had essentially stolen the vehicle. Then you’d have serious charges to hit the actual protesters with.
It’s not an easy question. Don’t do enough, it will just happen again. Do too much, and well it just won’t be Canada anymore! 