I'm in Zone 8b so far as I can work it out, and yes potatoes will survive overwinter in the ground, as tubers, and then grow away again in the spring. It's not frost that kills the top growth off at the end of summer, they just finish what they are doing and go dormant. I dug two up yesterday which were just starting to sprout, and I don't suppose that'll be the end of it. The major thing they have to contend with in the ground is slugs, so if I was trying to overwinter them deliberately I would be looking for slug resistant varieties. I grow Lady Christl and Red Duke of York.
I have a purple-skinned variety of Sweet Potato that has overwintered here in Zone 8; they've just started coming up in the past week. I don't know the actual variety name, though. These were grown from a potato from the store.