man this is what i would do. Stop any more destruction asap and go ahead and plan on taking them to court. Continue on with your plan on getting the city involved and start creating a paper trail with them to help you out. When they show up on monday be cool with them, explain the issues, tell them the city is involved, and tell them your demands. If you flip out on them, dont expect to them to be as willing to see their errors and correct the damage done. walk them through their crappy work, then tell them who's getting involved, then tell them that you want a return on funds and them to remove their work then tell them that you're already set up for a lawsuit and the ball is in their court. oh and if you have a way to, record that conversation that you'll have. That way if he agrees to take care of it, it's documented if he decides to pull out on the deal.
i know you wanted to get this wrapped up before winter, but at this point i'd hit the brakes on that. One thing to consider is lining up a good/known company for the spring and have it done right. Save all your receipts on storage costs for over the winter and bring that to court for this company you have now. It should be pretty easy for the judge to see their "workmanship", the distress it has caused you, and now the money you are now out for lawyer/court fees as well as storage fees.
I usually dont get into the suing people mode, but at this point I would and hit them hard. Only for the aspect that if you hit em hard enough financially, they might never be able to do this to someone else.