I saw Kim's exhibit a week or so ago and I found most of his work very impressive. Many of his shots seem to be composites of large numbers of individual images, probably combined in Photoshop. The ones of the DMZ are the ones that may be terrifically long exposures. I don't know what camera he used, but my guess would be that he used a very low ISO number, tiny aperture, and maybe heaps of ND filters. But since he does combine multiple images in other prints, he may simply have taken a whole series of more normal-length exposures, one right after the other. If he filled a memory card with 4-second exposures while the camera was on a rock-solid tripod, combining them would look like one heck of a long time exposure.
I'm sure he doesn't do his stuff hand-held!
Very interesting. I hope someone else can offer more authoritative information than my speculations.
P.S. The other current shows at the ICP are well worth a visit (Atget, Weegee, etc.). They have good shows there.