Blue Care Networks of Michigan, a subsidiary of Blue Cross Blue Shield of Michigan, has abandoned its attempt to purchase Physicians Health Plan of Mid-Michigan after the U.S. Department of Justice informed the companies that it would file an antitrust lawsuit to block the acquisition, the DOJ announced yesterday. Under the merger, DOJ said Blue Cross Blue Shield of Michigan would have controlled nearly 90% of the commercial health insurance market in the Lansing area and been able to control physician reimbursement rates in a manner that could harm the quality of health care delivered to consumers.