Yeah, my shelter (in Mississippi, where there actually IS overpopulation, if only regional) wouldn't be almost approaching "no kill" status if it weren't for sending dogs up north. We send mostly puppies, which apparently northern shelters don't have much of. My shelter probably gets in 5-10 litters of puppies every day, if not more. It takes forever to adopt out puppies of any size and shape here, especially black lab/mix pups, and from what I've heard, they get snatched up in northern shelters.
So if they can get adopted quickly in the north as opposed to dying here, why not send them?