For the elite? Come on. To do that you'd need a true revolution in DRILLING technology and it would be used for a LOT of other things besides mag-lev trains for just elites...
Who knows what's true. But there are persistent reports from a diversity of sources.
And some of the best researchers in the field believe at least some of such stories--especially between highly secret sites.
Oh, the ET's provided the slick drilling technology. I forget but I think it is some variation on a plasma drillhead somewhat akin to the big drill machines that drilled under the English Channel but a lot slicker.
It reportedly leaves the walls smooth as glass, if not literally glass.