As has been said, courses in Moose Jaw don't finish on time.
Changes have been made even in just the last year to try and increase production in Moose Jaw (more weekend flying, new syllabus, sim skipping, etc.), but the school has also been plagued with a number of aircraft maintenance issues this past year too numerous to discuss here, with the latest one rumoured to be reducing the number of Harvards on the line to 25% of the school's normal daily number (which I can barely remember what that number looked like) next week.
Take the particularly cold December/January and the ice filled November, and we've lost our fair share of ex's to weather as well.
If it's true that the incoming student tap has shut off, it's probably about time. Guy's are languishing here waiting to get on the line, not to mention the first half of the 08 series of courses still struggling to finish.
My next guess is Portage may well end up begging Moose Jaw for students as they will have their own slots to fill on PhIII courses.