The provincial health plans are required, by the federal legislation and funding arrangements, to cover all "medically necessary" treatments.
The term isn't defined in the legislation, and the provinces establish detailed fee schedules setting out what services are covered and what services aren't. If they try messing around with the definition, they're liable to a loss of funding, and that doesn't make the voters happy.
For example, a vasectomy or tubal ligation is covered; an attempted reversal is not. Prenatal care and delivery, and postnatal care, and so on, are covered in all cases; so is abortion.
No doctor ever has to consult an administrator or bureaucrat before providing treatment, ordering tests or xrays or scans, or prescribing medication. (Medication is covered by public plans in only a few provinces, but is covered for seniors and the low-income in the others.)
And doctors never have to argue about the price of their services, or chase insurers (or patients) to collect.
And the damn thing is ... it's way cheaper - for the public and for physicians themselves - to do things that way.
http://content.nejm.org/cgi/content/short/349/8/768The unfortunate perverse effect of this decision might be that physicians have less incentive to support calls for universal public-payer health insurance.