They do provide some information about their fuel economy test procedures.
Car Testing | Auto Test Center - Consumer Reports
My recollection of my time driving 4 cyl turbo cars was that they got good mileage if you dribbled along at low rpm off boost, but if you were on boost a lot the mileage was a lot worse. Maybe the CU tests involve more acceleration than the EPA tests. Which is more realistic? I don't know but I seldom hear anyone praising the EPA tests for realistically simulating real-world driving. In fact, when talking about hybrid mpg (e.g. Prius), people here quickly discount the EPA tested mileage.