I am not sure how it happened I actually can't even see the duplicate MAC address on the old VM, the MAC listed is different but the error when trying to update the new machine clearly states I can't do it due to a duplicate MAC address.
I can do a reverse update on things I NEED to change using the cloud interface so I'll probably keep things as they are MAC addresses wise sins you are correct it is historical information, it's just very odd all around, and thought id mention this so that it can be seen.