The CAT II / III holding points still all to do with autolands. When doing an autoland, the autopilots need to follow an uncorrupted ILS beam to the runway. These holding points keep taxiing and and departing aircraft out of the ILS critical area whilst aircraft are doing their approch.
The same sort of idea applies in the air with much bigger gaps between aircraft on the approach to ensure a good quality signal to follow.
On the 757 & 767 that I fly; a sustained deviation from the ILS above 200' or any deviation below is reason to call go-around.
There is not auto-takeoff, but we do use a PVD (para-visual display) which enables us follow the centre of the runway during a low vis take-off. The device gets its signal from the Localiser beam and displays a "go left" or "go right" indication. (display is a streaming barbers pole(!) - sounds strange but fairly intuitive for use). It is mounted in the glare sheild in front of the pilot so your vision can go naturally from out the window to the PVD as the visibility dicates. When the wheels are off the deck it closes up and your vision settles on to the instumrnts to guide your departure.
Clear as RVR 100m!
