If Musk wants to invest in speedy boring of 14' diameter tunnels, I'm all for it. IIRC, 14' is wider than the subway tunnels in London and Budapest, and only a foot narrower than in Moscow.<p>Modern subway designers would presumably balk at such narrow tunnels and subway cars, but if 14' tunnels are cheaper by an order of magnitude then maybe we just need to change our expectations and preferences. If they're an order of magnitude cheaper then it could even make sense for some cities with existing rail systems like SF to operate multiple rail systems.
Video mentions private ownership of necessary land as a problem; but it ignores possible legal solutions, such as compulsory acquisition of property (for public use, with just compensation); or vanilla negotiation.