Here’s how it will go:

1. The Boring Company aquires Amtrak.
2. Elon Musk says: “If we can’t come up with a better technology in X amount of years, we will just dismantle all the rail network and sell it a junk metal”.
3. The melting down of rails, etc., begins way before the deadline.
4. Elon Musk announces alternative in the form of self-driving cars, donates a few Teslas for charity.