The Postal Service has a strong case for union concessions
the law gives unions a veto over any reduction in their fringe benefits. Disputes go to binding arbitration, in which a panel essentially decides what would be a fair settlement. It does not have to take into account the impact on the Postal Service's financial condition.
Reference Source: http://www.washingtonpost.com/wp-dyn/content/article/2010/09/06/AR2010090603087.html