He served as guest commentator for a half hour. You can watch the entire broadcast over at TSN, but here's a highlight reel.
Some of his better quotes:
"Winnipeg is the Paris of Canada."
"Speaking of the hog line, I understand most of the teams eat a diet rich in pork."
The trials last all week and Sunday night was opening night, so there weren't really critical matches going on while Ferrell was in the booth.
The video: