[powera]

If this project makes financial sense, ideally an existing railroad company would run it.

Berkshire Hathaway (as the owners of the BNSF railroad) is the only US-based company that has the capital and railroad experience to even consider it.

In this situation, I'm not sure how or why the California government would turn away any foreign company willing to do it.

[khuey]

The project can make sense for the State of California in ways that are impossible for private investors. For example, providing fast convenient transport to places people want to go generally increases the value of land. The state can benefit from this passively via its taxing authority while a private investor would have to purchase land outright with an enormous capital outlay (if it were possible at all). HSR is also a substitute good for short-haul air travel, which is typically provided with government subsidy (in the form of airports).