I'd email CT and ask them.
http://www.calgarytransit.com/main/ct_contact_us.html
I know that is one of the reasons I don't park and ride.
And I can't see it being a cost thing. If they could fill an extra train, assuming it is full that is 474 passengers on a 3 car train; and at $2 per person (factoring in bus passes) that's just shy of $1000 in fares.