PAXboy,
If I understand correctly the dispute between DL/AA relates to the settlement when a pax is involuntarily rerouted from one to the other. This isn't something the MITA covers - it's either a bilateral deal, or the receiving airlines is entitled to what the delivering carrier would have got.
It's a pity because an interline agreement allows much more than invol reroute. Through checking of luggage being the most obvious but the ability to issue a single ticket/contract for a journey involving the other airline is where the consumer is going to get it in the ear.
Yes I'm a dinosaur, the days of airlines cooperating to make travel easier are long gone. Expect to see others bailing out of MITA because it isn't in their interests.