The Executive Office of Transportation has issued new regulations, 701 CMR 7, to allow the use of civilian flaggers instead of police details at some road construction sites. The regulations will become effective upon publication in the Mass. Register on October 3, 2008.
While the new regulations have engendered some controversy (see, for example, the Boston Globe's Unions Lose on Police Details), a report by the Executive Office gives the following results for a survey done in 1995 of all fifty states: "Forty state DOTs replied to the survey with thirty indicating that they used a combination of road flaggers and police details, and ten indicating that they exclusively used road flaggers. Massachusetts was the only state exclusively using police details."
Much more information is available from the Executive Office of Transportation's Road Flaggers and Police Details page.