As long as there is food, I'm sure hogs can survive. In the winter here, they have a lot and I mean a good fat layer on them. There's plenty running around in Tennessee and Oklahoma. Those states get cold. But its just like anywhere else, if there's a food source they will be fine.
Yes if the hogs have a good diet they will taste great. My uncle has killed hogs in Oklahoma and here in St. Augustine, Florida. The ones he got in Oklahoma he said you couldn't even tell the difference between that and a farm raised pig. He absolutely hated the Florida hog and the way it tasted. He hated it so much he mixes it with dog food and gives it to his dogs.
I can say the same thing for the deer here. They aren't that bad, but a Wyoming whitetail is simply amazing!
To the point, diet is everything.