I suppose they could change the way they interpret the rules. However I don't think they have a leg to stand on. The rules do not mention 'original flight date'. They state that you can change your booking up until 2 hours prior to departure and that mileage can be re-instating if you cancel a booking more than 22 days before the outbound flight departure.

"Changing Flight Rewards:
• Changes to the itinerary can be made at anytime up to 2 hours prior to departure subject to availability.
• If you cannot travel on your scheduled flights you must notify Aeroplan at least 2 hours before flight departure or your
ticket will be forfeit. Forfeit flight reward tickets are no longer valid for travel or mileage reinstatement."

"Reinstating Mileage:
• In order to return mileage to the account, the flight reward ticket must be cancelled at least 22 days prior to the scheduled
outbound departure date.
• Within 22 days of the scheduled outbound departure date the flight reward ticket is non refundable but changes (see above)
are permitted.
• The fee for this reinstatement is $90.00 CAD plus taxes per person per reward."

On the 2 occasions I had to do this I told the agent I needed to change my reservation and then cancel. I paid the change fee and moved the booking more than 22 days ahead. I then told the agent I wanted to cancel the booking. One agent was willing to perform both transactions, one was not and told me to call right back and have another agent perform the cancellation. The agents I had were fully aware of this 'loophole', but said it was within the rules as stated by Aeroplan.

Please let us know how this turns out. I would like to know if they are trying to take a new interpretation of the rules.