CO is ultimately responsible for adhering to their stated policies of getting passengers off the plane in a timely manner. And as the marketing carrier for the flight they have to be held responsible. They might not have been able to do something on the ground there, but they are still responsible for their customers.

I am happy to see that Mesaba is being held accountable for essentially being a group of idiots about the situation, though I do hold some concern that enforcement as "deceptive trade practices" in that regard is a potential slippery slope to tread down.