I just processed a refund on a Latitude ticket and thought to provide the detail for others that landed on this thread in the future.
After I click the Cancel link for my ticket in My Booking off Air Canada web site, on the very next page - at the bottom of the screen, I got:
Are you sure you'd like to completely cancel booking ABCDEF?
( ) Yes, and I would like my booking to be refunded
( ) Yes, and I prefer to retain any balance for future travel credit
Enter an email address (then re-type it, to verify) to receive confirmation of your cancellation, as well as an official refund receipt, where applicable.
Email* [email_address]
Verify Email* [email_addess]
Send email in which format?
( ) HTML (suggested format - includes graphics)
( ) plain text (if your email application doesn't support graphics)
[CANCEL MY ENTIRE BOOKING] button
After click on the button, you will get a confirmation screen - which you will get an email with the info in about 1 min. You will get another email with a PDF file that show the refund request/transaction. For me, this email with PDF can wait as long as 12 to 18 hours, for today, I got it in 1 min.