Massachusetts General Laws Chapter 272 Section 16 reads:
Section 16. A man or woman, married or unmarried, who is guilty of open and gross lewdness and lascivious behavior, shall be punished by imprisonment in the state prison for not more than three years or in jail for not more than two years or by a fine of not more than three hundred dollars.
As you can see this is a catchall provision, since it doesn't really define what is lewdness etc. So it is absolutely possible that he would be charged for the sex in public under this section.