It might be worth mentioning: Every year, usually about the 1st weekend in August, the Barcroft Station has an open house, during which the gate is opened and you can drive all the way to the station and start from there. (It's easiest to find parking there if you have a high-clearance vehicle.) Useful if you want to shave off a couple of miles of just road trudging... AFAIK, however, the summit 4WD road is never opened to the public for motorized travel.
As I recall (we did the climb on Sunday, Aug 5th '07) we'd heard about it, and then they had the information on their web site:
I'm assuming it's still an ongoing thing. They had a medical station set up in the summit hut, where you could volunteer to have your blood oxygen, etc., checked! Unfortunately it was already a half-hour wait when we got to the top, and we couldn't stick around.
"After the first glass, you see things as you wish they were. After the second, you see things as they are not. Finally, you see things as they really are, which is the most horrible thing in the world."
--Oscar Wilde on Absinthe