I'm interested to see this tested on Jan 1; have 2 people at the same medallion level buy a ticket within the check-in window. One buys MC, one buys C+ and see where they fall on the upgrade list. Theoretically they'd have the same coach fare class, but should check to make sure. Then, have person that paid MC buy a C+ upgrade and see if they jump up the list. Finally, cancel for a refund.