Massachusetts General Laws Part I. Administration of the Government (Ch. 1-182) Ch. 6C, § 27

(a) The exercise of the powers granted by this chapter shall be in all respects for the benefit of the people of the commonwealth and for the improvement of their health and living conditions and as the operation and of the department  1 shall constitute the performance of essential governmental functions, the department shall not be required to pay any taxes or assessments, except as otherwise provided by this chapter and the notes or bonds issued under this chapter, their transfer and the income therefrom, including any profit made on the sale thereof, at all times shall be free from taxation by and within the commonwealth.

(b) The lands and tangible personal property of the department shall be deemed to be public property used for essential public and governmental purposes and shall be exempt from taxation and from betterments and special assessments.