Thank you all for your comments. Based on the feedback here, I wrote a note to AC in mid-August. Just today we received the following:
We are pleased to advise that a refund of $ 25.00 USD per ticket was processed today and that detail has been sent to the credit card company.
What we find is that the credit can take another 1-2 statements before our customer sees the refund . You may however be able to see the transaction within 3-5 business days if you do online banking. Refunds must be processed back to the same form of payment that paid for the ticket.
If you still haven’t received your credit, please call the credit card company and advise them what date Air Canada processed your refund.
If you find that you still require assistance, please do not hesitate to email us back and we’ll gladly investigate further.
Our hours of operation are Mon-Friday 0700-1500 CMT.
Thank you for contacting the Air Canada Refund Services department.
So it took almost 4 weeks, but they did the right thing in the end. Also, I should mention that on the return trip, they encountered a similar situation in YVR but the AC agent was professional and friendly and on her own accord asked for a supervisor. Even the supervisor was confused why the A3 number wouldn't 'stick', but was happy to over-ride the system so no payment was necessary.