I wouldn't describe that as chaotic and running riot. I walk my lurcher every day on the footpaths round our house. He runs off the lead, sometimes up to two fields away from me, but he comes back instantly I whistle or call, as if he's on a piece of elastic. BUT there is no doubt that if he spots a rabbit, then he is off and I almost certainly won't be able to stop him until the rabbit is caught or disappears (usually the latter, he is not a very good lurcher!). So there is a risk that he could run over a road or through someone's garden, but it is a small risk and one that I take in return for a happy dog who has the freedom to exercise his natural instincts and is well exercised. The alternative would be to have him on a lead or at heel all the time which would lead to quite a fed up hound.
Foxhounds are the same. The relationship a huntsman has with his hounds is incredible. He might have 100 or so in kennels, and 30 or so out on a hunting day, and he (or she) knows every one by name, and each hound's family tree, personality, ailments, strengths and weaknesses. It is amazing to watch a pack of 30 odd all sitting looking up at their boss waiting for their next command. When they are hunting they go where their huntsman asks them to and are amazingly controllable, but once they are on a scent then they are following their natural instincts. A huntsman can call them off a scent, but if he is not quite quite quick enough (and they are fast when they start running!) then sometimes it does happen that they will go places where they shouldn't.
I think, similar to me when I'm walking my dog, they will do what they can to plan the day carefully and stay up with their hounds, but occasionally things don't go to plan and that is a risk that they take, and when incidents happen like your fence getting broken then they do (or should do) everything they can to apologise and make amends. (Definitely get in touch with the hunt in question, tell them about the damage and ask them to fix it).
Generally hunting takes place in areas where there are very few people, so it can mostly carry on without causing anyone else any problems, but when it comes into contact with people and towns there is no doubt it seems like a complete anachronism. We are all so used to living with systems and rules and hunting does not seem very compatible with a world of risk assessments and litigation. Which is part of why I think it is utterly magical!
(As an aside, I have had hound puppies living with me a few times, and actually they were never that interested in my cat! unlike the lurcher....)