Section 15G. (a) An entity that may invest pursuant to section 15A or the legal list may invest in bonds, notes or other interest-bearing obligations of a gas, electric light or water company incorporated or doing business in the commonwealth and subject to the control and supervision of the commonwealth.

(b) An entity that may invest pursuant to section 15A or the legal list may invest in the bonds of any company which at the time of the investment is incorporated under the laws of the United States or any state and transacting the business of supplying electrical energy or artificial gas or natural gas purchased from another company and supplied in substitution for or in mixture with artificial gas for light, heat, power and other purposes or transacting any or all of the business. The bonds shall be part of an original issue of not less than $25,000,000 in principal amount.

(c) Not more than 25 per cent of the assets of the entity shall be invested in obligations under this section and no more than 4 per cent shall be invested in the obligations of any 1 company.