Section 2B. Action of tort for damages arising out of any deficiency or neglect in the design, planning, construction or general administration of an improvement to real property, other than that of a public agency as defined in section thirty-nine A of chapter seven shall be commenced only within three years next after the cause of action accrues; provided, however, that in no event shall such actions be commenced more than six years after the earlier of the dates of: (1) the opening of the improvement to use; or (2) substantial completion of the improvement and the taking of possession for occupancy by the owner.
Actions of tort for damages arising out of any deficiency or neglect in the design, planning, construction, or general administration of an improvement to real property of a public agency, as defined in said section thirty-nine A shall be commenced only within three years next after the cause of action accrues; provided, however, that in no event shall actions be commenced more than six years after the earlier of the dates of: (1) official acceptance of the project by the public agency; (2) the opening of the real property to public use; (3) the acceptance by the contractor of a final estimate prepared by the public agency pursuant to chapter thirty, section thirty-nine G; or (4) substantial completion of the work and the taking possession for occupancy by the awarding authority.