If the Desert Xpress route is funded, built, and eventually fails, who would own that railway? Would it be a valuable asset for some entity?
Regarding the Desert Xpress loan, Government loans, by their nature, are partly partly financial and also partly "industrial policy" to encourage certain industries, such as "made-in-america" rail cars etc. One would expect a higher failure rate than traditional loans because of this dual purpose.
Regarding Solyndra, etc. every lender, government or private, MUST make "bad loans" occasionally. If a bank never made a bad loan it would be out of business, because every loan carries some risk, and if a bank never took any risk, it would never make a loan.
So, how does one evaluate and limit risk of failure of any loan, and in particular a one-of-a-kind railroad project. . .