I don't know the OW rules as well, but *A RTW tickets have SITI (Sold Inside Ticketed Inside) rules that require you to have the ticket issued and purchased there or they charge you the greater of the price there and where it is actually sold. Canada is an exception for some Canadian rule -- you could buy it there and have it start anywhere at the price of there. If that sticks for OW then you could get a Canadian travel agent to do it for you and get the MLE price (you still have to start from MLE).