I think keeping maintenance work within the scope of the union instead of the realm of outside contracting is a perfectly fair ask from the union. Particularly as automation is becoming more of an issue keeping control of that maintenance work will likely become a matter of life or death for the union workers' employment. I'd go so far as to say trying to make maintenance the realm of outside contractors is a sneaky way to try and bust the union long term.

That aspect of the contract almost seems like nothing and yet that it is such a sticking point for both parties ought to be very telling.