When a close call like last week's train derailment in Beacon Hill happens, the "what if" questions — as in what if a deadly poison had been released near so many homes — soon are followed by questions about what can be done. But answers to how long it will take to reroute most trains out of San Antonio's core, how much it will cost and where the money will come from don't come easily. And the best guesses on fixing the problem — a decade or more and billions of dollars — don't help people sleep much better. "It's...