"Social Movement" Unionism has proven...

to be an absurd framework through which to understand labor's political identity in the 21st Century, in my opinion.

but some interesting issues come to light as one goes about taking that framework apart. par example, see Paul Johnston's Success While Other Fails; Social Movement Unionism and the Public Workplace (1994):

This does not mean that public workers’ movements will promote a “workers’ state,” abolish capitalism or the state, and so on. Different parts of the public workforce are likely to be implicated on different sides of every great social contest. The important point is that public workers' claims are framed in certain common forms and that these workers rely on certain kinds of strategic resources; beyond that, the significance of a particular movement depends on its historical context. As they frame their interests as administrable public interests, they are perhaps the quintessential “state-making" social movement.