It can scale to a whole province of 5 million people.
I had Kaiser Permanente when I was in the US. Now that I'm in BC, Canada, it is very similar. I walk into any hospital in the province and every doctor and specialist in the building are part of the same system (technically they are broken up into three geographic subunits, but to the patient it basically doesn't matter). If I need some sort of treatment that hospital doesn't offer, they can immediately refer me to the correct hospital. For emergency cases the provincial ambulance service will transport you to another hospital by road or air at no cost.
There are still independent specialists and doctors outside of the hospital system, but they have access to the same records systems and the billing is so seamless that I suspect that most people don't realize it is happening since it never involves the patient outside of providing your ID.
I had Kaiser Permanente when I was in the US. Now that I'm in BC, Canada, it is very similar. I walk into any hospital in the province and every doctor and specialist in the building are part of the same system (technically they are broken up into three geographic subunits, but to the patient it basically doesn't matter). If I need some sort of treatment that hospital doesn't offer, they can immediately refer me to the correct hospital. For emergency cases the provincial ambulance service will transport you to another hospital by road or air at no cost.
There are still independent specialists and doctors outside of the hospital system, but they have access to the same records systems and the billing is so seamless that I suspect that most people don't realize it is happening since it never involves the patient outside of providing your ID.