Just throwing this one out into the wild yonder: Is there anything (legally or otherwise) to prevent Amtrak from running buses on the Cardinal and Sunset Limited's off days, clearly marked and forewarned of course, such that some form of daily intercity service is provided, while simultaneously gauging passenger demand for a daily train? Amtrak California is restricted by law from selling bus trips that do not connect to a train, but is there any such restriction upon Amtrak itself?