That is a very interesting question.
In arbitration, the tough decisions in the final settlement are left to a third party, while in a negotiation, when there is access to the right to strike, you are essentially obliged to come to an understanding. So it is a matter of meeting each other halfway, according to the view that the union may take, according to its reading of the facts, in terms of its negotiating power and its power to choose.
That is how I would answer your question.