It's hard to know the exact rules, but the general idea is that the conductor or director provides cues to individual and/or groups of players, who either perform a specific pre-scripted musical passage or do an improvisation. The technique was popularized by John Zorn, but it's similar to things Frank Zappa was doing in the '60s, and also to Butch Morris' practice of "Conduction." The results are too random to predict, but when it works, it can be both great and hilarious.
By that standard, the set worked wonderfully. Derome, beginning a year-long celebration of his 60th birthday, started on a very high note. The work — simultaneously controlled and anarchic — was a wonderful testament to his continuing importance as a leader of the Quebecois new music scene.