I did get a refund, yesterday, for a trip this evening. The new itinerary from AC stated
AS A RESULT OF THE ITINERARY CHANGES YOU REQUESTED, A TAX REFUND HAS BEEN PROCESSED TO YOUR CREDIT CARD IN THE AMOUNT OF: CAD 40.00
I have no idea what itinerary change prompted this, as I was charged the full 55.00 + GST for the initial change. However, AC does give back!