I would tend to agree with Mr Bolt re sending engineers across the continent to cover for a flawed roster. As long as these blokes are not carrying out reciept/dispatch duties, it just proves that the current roster does not work. This is something that should stand up and shout at not only Big M but his superiors as well.
I think however that we need to understand that the position of Duty Maintenance Manager (DMM) is a management roll and save for a few individuals is an extension of the Big M's iron fist no matter where they are stationed. I would even doubt whether many of them are even members of the association any more, so by working a 12 hour roster they would definatly not perceive any conflict with the rest of the guys, they would not even aknowledge themselves in the same group, they are managers.