“Hospitals would do that at their own peril, as their relationship is symbiotic”
I don’t think so. Bamys plan is to have a single payer system in which all docs will ultimately work for the government. One of the easiest ways to do this will be to prohibit docs from having privileges at hospitals unless they are willing to accept government payments.
In the US, with the rise of satellite and specialty outpatient services, many (most?) Doctors can often forgo the need to associate with hospitals at all. Several Doctors friends of ours don't practice in hospitals (primary care, allergists, pediatricians), and others are there infrequently (OB-GYN on call).
However, I can't underestimate the power of a coercive government.