Read the paper more closely. I do not know if they use it, but they do have access through the Kaesong industrial region.

According to Wikipedia (http://en.m.wikipedia.org/wiki/Kaesong_Industrial_Region), Hyundai built it, so they know of its existence.

Actually, unification might make this less attractive, as wages likely would rise in the North, changing the economics of doing this kind of stuff (I guess a bit in the way the abolition of slavery changed economies)