You'd think they'd pick something more interesting to photograph though wouldn't you?
I don't think that you could really refocus for every shot as you'd almost certainly have a problem stitching frames. Surely you could only do this via a fixed focus position (infinity or hyperfocal).
They actually acknowledge in their description that suitable subjects are hard to find in the Netherlands! Still, it is the classic "brick wall" resolution test, once you zoom way in.
About focus, I disagree for two reasons, but am not completely sure.
Mainly, depth of field. Think what would happen if you focused the 400mm, f/22 lens used here at one distance and then photographed various subjects at the wide range of distances occuring in this image: could you get them all in focus as sharp as seen here? For the D1X, using this DOF calculator
http://www.dofmaster.com/dofjs.htmlwith its suggested circle of confusion of 20 microns, the hyperfocal distance is 354 metres, and focusing at that distance gives an in-focus region from 177 metres to infinity. Bear in mind that at the limits of this standard DOF, sharpness is below optimal, because the CoC of 20 microns is distinctly bigger than the actual resolution limit of the D1x's pixel size.
The nearest subjects seem to be less than 177 metres away, and it all looks sharp from there to "infinity", so there seems to be more DOF than a single common focal distance could achieve.
Also, they acknowledge some noticable patching glitches, and the focus changes on neighboring frames would generally be slight enough to fit within these imperfections.