Harvard researchers have found something that looks a whole lot like their unicorn: An ACO that is up, running and looks to be delivering the exact results everyone has hoped for. Blue Cross Blue Shield of Massachusetts spent years paying healthcare providers for each service they provided, just like the rest of the healthcare system. Three years ago, they offered doctors a payment model that looked a whole lot like an ACO. This project is called the Alternative Quality Contract. In yesterday's Health Affairs, a team of Harvard researchers published a long look at how its been doing—and it looks to do be doing pretty well.