News story on a vérinage demolition that has been posted already, but with new, slow motion views and a look at the setup: http://www.dailymotion.com/video/x2td63_hd20h20070822chunk2_news
As they say - you remove structural elements (external walls of part below, etc) so that the remaining building is like a 'house of cards' and then it is very easy to destroy it with hydraulics, etc. as seen.
So what you see is a partially dismantled structure (a 'house of cards') given a little kick so it collapses.
We French are really clever.