Last month, a superior court judge rejected a proposal for Partners HealthCare to acquire three hospitals in Massachusetts. But that hasn’t stopped Partners — it’s now in the process of taking over a smaller medical practice on the South Shore.

Harbor Medical Associates has about 70 physicians in a few towns along the South Shore. Partners wants to bring them into its network of 10 hospitals from Nantucket to Northampton. Paul Hattis of the state’s Health Policy Commission says he’s concerned — not so much with the number of facilities Partners owns, but with Partners pulling more doctors – and their patients — into an already expensive system.

"Hospitals are bricks and mortar but it’s physicians that refer patients and pull lives into a system," Hattis said. "In many ways this is much more about the physicians and getting relationships with them than it is about the hospitals.”

Partners would have pricing power on the South Shore because it has little competition in the region. But it also invests millions in facilities and doctors, and runs teaching hospitals. The state health policy commission says Partners is getting too big. And although the attorney general oversees Partners mergers, she says she doesn’t have a case to make for an antitrust suit. Hattis acknowledges this, but says there’s a larger policy issue at stake: Mergers mean doctors can’t always send patients where they’re best served — clinics, community hospitals or larger medical centers.

“The real policy challenge is: Is there a way to get doctors between the community and academic medical centers working effectively in a team-like way, but not necessarily having an ownership model or an economic model that incentivizes people either to do more or make referrals to certain locations?” he said.

Partners says it “will improve patient care in the South Shore region, and can better coordinate patient care,” especially for those who travel to its larger, Boston hospitals. Right now Partners is still in talks with Hallmark Health System, which operates hospitals in Melrose and Medford. These hospitals welcome the investment from Partners. Now it’s not clear how the Harbor acquisition might affect their chances of joining.