Being a federal mandated program all Canadian legal residents( not just citizens) are covered*. There have been attempts by at least one Province to have a two tier system. The Feds shut that down pronto. You can of course drive or fly to any other country for your medical needs and pay out of your own pocket. Our system isn't perfect, not by a long shot but it is better then nothing and far better then some of the European plans.
As I understand it, your HMO(?) allow funds for the symptoms but not for the cause, which is not the case here.
Canadian politicians are covered as well but it would be a given that there is no waiting line for them since they have access to military facilities if needed.
While living in British Columbia the Medical Services Plan did send folks for treatment across to Port Angeles( WA) if the waiting list was to long at no cost to the patient.
*nobody is going to force you to use it or sign up however if you have to start paying out of your own pocket for all doctors visits and hospital stays you will see the error of your ways in a hurry
T