@Dan Rollman, the inspiration came from a small segment of an (awesome) OK GO video : http://www.youtube.com/watch?v=qybUFnY7Y8w
It took quite a few days to get the system working correctly and a couple of days to prepare all the mouse traps...
@Simon This i an official festival with the presence of the City maire and all. Completely true though, they are pushing it with the over numbered firemen. They take it as a kind of exercice and public presence.