Otterman, in the US, at my airline, we do it just as you described. "Fail-Operational" for Cat IIIb and "LAND 3" annunciated, but "Fail-Passive" and Cat IIIa for "LAND 2/NO LAND 3".
I recently did a CAT IIIb into SEA where they were reporting 200 ft and 1/2 mile. We were suspicious of it, and set up for CAT IIIb Autoland. We did'nt see anything at 200, 150, 100 or even 50; at about 30, I saw the runway, and shortly after, a smooth rumbling announced our arrival onto the runway. As other aircraft were missing their approaches at 200 ft.DHs, we informed the controller that it was definately NOT 200 and a half mile!
Use it if you've got it!
