Having done my time in health care startups with an emphasis on billing and reimbursement flow, let me say that I would have been overjoyed to have been put out of business by single payer (or by a U.S. version that, like Medicare, would be "single, multiple private administrators"). Medical billing is just an utterly perverse environment to deal with, and the Feds were the only player who would consistently tell you exactly what to bill, how to bill, and why to bill it that way.