Section 5C of said chapter 12, as so appearing, is hereby amended by striking out paragraph (3) and inserting in place thereof the following paragraph:-
(3) When a relator brings an action under said sections 5B to 5O, inclusive, a copy of the complaint and written disclosure of substantially all material evidence and information the relator possesses shall be served on the attorney general pursuant to Rule 4(d)(3) of the Massachusetts Rules of Civil Procedure. The complaint shall be filed under seal and shall remain so for 120 days after service upon the attorney general. Notwithstanding any other general or special law or procedural rule to the contrary, service on the defendant shall not be required until the period provided in paragraph (5). The attorney general may, for good cause shown, ask the court for extensions during which the complaint shall remain under seal. Any such motions may be supported by affidavits or other submissions under seal. The attorney general may elect to intervene and proceed with the action on behalf of the commonwealth or political subdivision within the 120-day period or during any extension, after the attorney general receives both the complaint and the material evidence and information. Any information or documents furnished by the relator to the attorney general in connection with an action or investigation under said sections 5B to 5O, inclusive, shall be exempt from disclosure under section 10 of chapter 66.