Years ago I went through something a little similar in that my 3-yr-old girl just did not want to use the toilet. Her preschool teacher told me to leave her alone and act like I didn't care about it. As soon as I did that, within a week she was completely trained. The deal was, it had to be HER idea instead of mine! It's a control thing when they are that age. Basically, your little guy is trying to control the only thing he can--he had no choice about moving, his daily routine is governed by you (as it should be)so the only thing he can decide on his own is when and how to potty. (I'm not doctor but it makes sense) Anyway, here's what I would do. Take him shopping and let him choose his own underwear. Let him know it's his choice to decide all on his own. Tell him he needs to wear the underwear at home, but that if he's more comfortable he can wear a pull-up when you go out. When you're at home, use an egg-timer set to go off every hour. Let him set the time with you. Tell him when he hears the bell, HE can decide if he needs to go or not. It's all up to him. Then, get him his own little bucket, sponge, and mop. Tell him they are his cleaning supplies, to use when he has an accident. Tell him that you will help him if he needs it, but than when he decides not to use the potty and then has an accident, it will be his job to clean it up (obviously you'll go in after him when he's not aware and do a "proper" job of it.)
I would also start letting him have a few choices about what his daily routine is like--certainly not letting him rule the roost, but sort of giving him a chance to feel like he has some sort of control over his environment. Let him pick out his own clothes (even though they might not match)Ask him to choose between two things rather than giving him an open choice because that's too much to process, but say "Do you want to watch Dora or Sesame" or something like that. Let him help you make lunch. It will be messy at first but he'll feel like a big boy and that will help him feel like he can take ownership of using the potty.
I'm not advocating giving a toddler a whole lot of leeway--just thinking that a few simple choices he gets to make will help him feel less out of control.
Besides, I would venture a guess that as soon as he realizes what a pain it is to clean up his accidents, he'll decide it's just easier to use the pot.
Hope this helps you out. Just remember, he's not going to go to kindergarten in diapers!!! Good luck...