The exemption that the insurance industry has extends only to insureds. Insurance companies do not have an antitrust exemption in dealing with providers. The exemption is limited to the business of insurance, as defined by the Supreme Court and in the McCarran-Ferguson Act. As far as the eye can see, courts have confused more issues than they have settled. In many cases, even conduct such as price fixing among insurers has been protected.
Federal regulators defer largely to the states.
The insurance commissioner or attorney general's offices have historically given insurance company combinations a reluctant blessing. The big smoking gun would be who is being helped and who is being hindered by the proposed relationship. You may be hindering physicians, but there's some presumption on the part of the state that you're helping to keep health care prices down and you're not negatively impacting access to services, for the most part. I think that was the main problem with it. There are also concerns expressed by the Federal Trade Commission and the Department of Justice that the price of health insurance would go up, that there is a great potential for abuse by health care providers to raise prices, and that the price for health care in general will go up.