I used the Turboclair at CDG a few times in the late 70s and early 80s. As far as I recall they "guaranteed" 200m(?) vis in the touchdown zone and therefore didn't give touchdown RVRs. It had to be switched off as the aircraft passed 1000 or so on finals so the "crosswind blast" could dissipate. Always worked for me ok (vis was always better than the guaranteed level) although at night it was essential not to use landing lights, as going into the wall of fog at the end of the cleared area with lights on could be quite an experience. (Mind you I've always found it better to land at night without lights if the RVR is less than about 300m)
On a slightly different topic does any body else remember the ice clearing operations at Moscow SVO in the 70's? To clear the ice from the apron they had what looked like cement mixer lorries with old IL62 APUs strapped to them pointing downwards at 45 degrees. The exhaust blast would free areas of ice inches thick and about the size of a dining room table. These would go tumbling across the apron smashing apart. The noise of a couple of these going at full blast made even a Trident seem quiet.