I don't know about a permanent, long-term solution but maybe for the moment you could at least hop the fence one night and line the bottom of the cages with old blankets/towels, some straw, or something similar. I'm sure if it was there the owners wouldn't bother to remove it and you may feel somewhat better about it.
Years ago my neighbors had a beautiful Golden Retriever puppy. They didn't abuse him but they paid absolutely no attention to him whatsoever (which in my opinion is close enough). He had a fenced yard but for some reason was still tied to the porch 24/7. I always peeked over to make sure he had fresh water which he often didn't and at night I'd hop the fence and bring him over to play with Bud and Tash. We'd all have a good game and I'd give him some treats, then sneak him back "home". They ended up giving him away (presumably) as I came home from work one day and he was gone, I can only hope he ended up somewhere better! It might sound silly to sneak him over, but there was no talking to these people, we had numerous problems with them long before the puppy showed up.
If people don't want dogs, why do they continue to get them??!!