As I have worked at Intl tkting I too wonder the same thing. We never know when and how they are going to open up the seating on an aircraft. Being Intl it does make the seating more difficult as most of out Intl flts are now codeshares with other carriers.

Now if that is the case, one airline gets a certain number of seats and Delta gets the rest if it is our plane. There is no way to determine who has the exit row seats us or the other airline. The other carrier assigns seats on their computer which is a different system from Delta. Then the res are transferred over to the Delta computer with the seats previously assigned.

I cant tell u how to go about getting an exit row seat but that is how seating works over all with a codeshare which seems to be the case for u. Sorry