I don't know much about unions, I admit. But, I offer these this counterpoint: The proposal is to use elevated tube on pylons. The pylons are likely to be of

I don't know much about unions, I admit. But, I offer these this counterpoint: The proposal is to use elevated tube on pylons. The pylons are likely to be of a regular design, probably made with steel molds. The amount of skilled labor to build them is likely to be much less than building overpasses. Musk has said that the tubes would be built in 30m segments in a factory, and welded in place. Given Musk's experience with robot assembly at Tesla (watch http://kottke.org/13/07/how-the-tesla-model-s-is-made http://kottke.org/13/07/how-the-tesla-model-s-is-made), my guess is that much of the construction of the tubes, and the rebar mesh for the pylons will be automated. Making stuff in your factory as much as possible means you can automate more. It doesn't eliminate the labor, but it does reduce it a long way.