It's not clear to me that he is interested in being the one to build it. I think he wants somebody else to.

I'm sure he'd prefer someone else do it but then again he might have preferred that someone else would have conceived of and designed it -- or something similar. There's a chance, as with the leadership of Tesla, that no one else with the capability (or position/reputation) to execute will be found, and I'd be surprised if he were not heavily involved in seeing it through.

From what I understand he still sort of wants out of Tesla in the long term. SpaceX is his baby and he's only running Tesla because he feels that he has to. I suspect he isn't receptive to spreading himself out over a third project (he apparently doesn't do much work himself for SolarCity).

My bet is that people in the middle who don't get any benefit from it will prove just as obsrtuctive as they are towards any other large scale infrastructure project.