I can't see ST being returned, it would be a major concession by the company
I disagree, I think if the LT believe that returning ST (as part of an agreed settlement) will end this dispute then it will be returned.
I'm aware that in doing so lots of 'backing BA' types will wail and gnash teeth, however you can't have it both ways. Numerous statements to the effect that it is BA's trainset and they must be allowed to manage it as they see fit apply just as much in this example. If it's in the best interest of the company and the shareholders to return ST, they will do so.