The union wage premium, revisited

Ezra Klein, in his response to my post on the union wage premium, directed our attention to this article about the union wage premium in service industries.  The paper does find a wage premium, and in doing so offers up some juicy bits:

Our research suggests that unions usually have little power to inhibit subcontracting altogether, but that they can sometimes mitigate its negative effects on their members.  The hardest trend to fight has been the outsourcing of labor-intensive kitchen tasks – baking, cleaning and chopping produce, making stocks and sauces.  The purchasing of prepared foods has become such a ubiquitous and fundamental business strategy in the industry that it has been almost impossible for unions to stop it.  In the end, the economics of using pre-prepared food are simply too compelling, and because the outsourcing is usually done piece-meal, the union would have to fight over just one or two jobs at a time.  However, when the numbers of jobs involved are bigger and the economic advantages less clear – for example, subcontracting an entire laundry unit – unions have been able to focus their efforts and have had somewhat more success, slowing the process down or limiting it.

Yes I can see the resulting wage premium within the union, but is this a good way to advance the state of the working man in the United States?