I spoke to a guy that worked on the initial planning and implementation of their IT system. It was after a couple beers, so I can't remember everything he said.
But, he recons the cameras CAN see your license disc even at 160km/h.
Very high resolution cameras are used- 3 per lane, and they compare their images to resolve the picture.
I can't remember the exact figure, but they store quite a few Peta bytes per day! That's why they only keep the pics for 30 days.