It's not rocket science is it? You just pedal like buggery when you get a chance, and lean the bike over as far it will possibly go round every corner. Job done.
I think Fabian was having some fun for the cameras on this descent, there's some pretty OTT cornering going on, especially when he gets back to the bunch at the very end. Impressive nonetheless.
Youtube have stopped embedding of this vid, so just watch it by following the link http://www.youtube.com/watch?v=j_wEG2RNMJc