In 2002 the offensive coordinator for the Oakland Raiders was none other than Marc Trestman. The Raiders went 11-5, lead the league in total offense, and went to the Super Bowl (and lost). Trestman left the team after the 2003 season, and the Raiders haven't been better than 5-11 since, and its offense has been perennially anaemic. He moved on to the Dolphins and helped that team to a winning record, and then to N.C. State as O.C. in 2005. The Wolfpack went 14-0 that year.
The point is that wherever Marc Trestman shows up the team improves. The Allouettes are no exception. He's clearly a great coach and the CFL is lucky to have him.