Mass. Gen. Laws ch. 175 § 111A
Two or more companies may issue a single policy of insurance against loss or damage on account of the hazards specified in the third clause and in subdivisions (a) and (b) of the sixth clause of section forty-seven on which each company shall be severally liable for a specified percentage of any loss or claim. Such a policy shall be executed on behalf of the companies by a duly authorized person and the corporate name of each of the companies shall be affixed thereto.
No such policy shall be issued or delivered until a copy of the form thereof has been on file for thirty days with the commissioner, unless before the expiration of said thirty days he shall have approved the form of the policy in writing; nor if the commissioner notifies the companies in writing within said thirty days, that in his opinion the form of the policy does not comply with the laws of the commonwealth specifying his reasons therefor; provided, that such action of the commissioner shall be subject to review by the supreme judicial court, nor unless it is headed by the corporate names of all the companies; nor unless it contains in substance:
Notwithstanding any other provision of this chapter, two or more stock companies or two or more mutual companies may issue a single policy of insurance against legal liability for loss or damage to person or property caused by nuclear energy hazards on which such companies shall be severally liable for a specified percentage of any loss or claim. Such a policy may be executed on behalf of the companies by a duly authorized person and need not be countersigned by a resident agent of more than one of such companies in the commonwealth. Such a policy need not be headed by the corporate names of all the companies provided the corporate name of each company is affixed and need not include the provision numbered (5) in section one hundred and two A. In lieu of the provision numbered (1) in this section, such a policy shall plainly specify the percentage of any loss or claim for which each such company shall be liable, and, in lieu of the provision numbered (2), such a policy shall include a provision that any notice, sworn statement or proof of loss which may be required by the provisions of the policy may be rendered, made or given to any one of such companies or to the agent named in the policy as the duly authorized agent of the companies, and that such notice, sworn statement or proof of loss so rendered, made or given shall be valid and binding as to all of such companies. Such a policy shall be subject to the provisions of this section except as otherwise provided in this paragraph.
Nothing in this section shall permit two or more companies to issue a single motor vehicle liability policy as defined in section thirty-four A of chapter ninety.
In the event a company or filing or rating organization eliminates or reduces certain coverages, conditions or definitions in such policies issued under this section, the company must attach to each of such policy a printed notice setting forth what coverages, conditions or definitions have been eliminated or reduced. If explanations of such reduced or eliminated coverages are not contained in such a printed notice attached to such policy, then such coverages, conditions or definitions shall remain in full force and effect without such reductions and eliminations.
Mass. Gen. Laws ch. 175, § 111A