This is one reason I'm in favor of government health care: The profit motives of private health care favor denying care, since not paying out money is a good way to make money. So you have case where nobody will cover you for arbitrary reasons, or deny you payment due to a "pre-existing condition" or some other nonsense.
As for power lines.. well, there haven't really been any conclusive studies in this area. But you get the point.
Same-environment shouldn't be a factor, as long as the reasons the environment might impact health are/can be known.
I'd argue that nobody should be living somewhere that might have health risks involved (e.g., underground oil spills, toxic ash, a radioactive waste storage facility a block away from the elementary school .... in other words, williamsburg/greenpoint brooklyn).
This is an argument against all private insurance (home, auto, etc).
Would you favor the nationalization of all types of insurance or just medical? Doesn't auto-insurnace have the same evil profit motive?
What stops a business from giving her 75% of the $12,000 they currently spend on her benefits, pocketing the difference as increased profit, and leaving Sally to make up the difference with her dwindling discretionary income (despite a pay raise). I'm not sure how this help Sally.
I.e., Sally will go work somewhere else, or will unionize and kick their ass (ideally only in the figurative sense).
There's a lot of assumptions built into that outcome, but I take it that's the idea, if the numbers work out.