Tech, so far, has not demonstrated any interest in actually investing in things outside the tech sphere. There's private philanthropy going on (Gates Foundation), but very little in the way of interest in domestic civics. No one has done anything comparable to the Vanderbilts and Carnegies launching universities.
There are fundamental differences, anyways. Tech can be scaled up without much interference or perceived negative impact to neighbors, and tech's main roadblock has been tech itself. Transit's main roadblock is politics, not technology; people are loath to raise more taxes, people don't like "those characters" having easier access on the train, they'd never ride a train so why should they pay taxes for one, etc.
TX Central has been trying to launch a high speed rail project for years now, and they've mostly received a never-ending stream of lawsuits for their troubles.