I like how Musk can say just a tiny bit more than absolutely nothing and get everyone to freak out.
Approval? From whom? Approval for a 250 mile tunnel between two major cities is not given verbally, thats not how things work. And for a technology that remains entirely conceptual and unproven, no less. Can he build tunnels before he knows how big he needs to build them, and what support infrastructure is needed? Can he build one before he knows what kind of alignment the hyperloop needs? Somehow I don't think so. Keep in mind this is also more than double the length of the longest tunnel in the world.
I'm not sure how things work in the states, but I'm not sure a project like that can be undertaken like that. You'll be digging under land you don't own - the government can do that, can a private corporation? Especially when an alignment has not been published nor decided on. Never mind the environmental approvals that somehow I doubt have been done. Does the public get no say in this (maybe not, since its a private venture...?)? How does he plan on funding this? Whats his timeline, and whats the basis for that timeline, given that the technology remains unproven? And no, don't tell me he's going to build a 250 test track, I don't believe you.
My problem with Musk is that he can at times feel very click-baity; he likes talking big and riling people up yet theres absolutely nothing here other than his extremely vague word. From what it sounds like, he doesn't have political approval, he has political support, which is completely different.
As always on HyperLoop, I hope to be proven wrong, but I remain a firm skeptic.