Section 27. There shall be a mutual exchange, between the council and all offices, boards, commissions, departments, divisions and agencies of the commonwealth, and all offices, boards, commissions and departments of each political subdivision of the commonwealth within the district, and all public authorities operating within the district, of data, records and information within their knowledge and control pertaining to the district, or to parts thereof, which may be required for the preparation of plans made pursuant to section twenty-five; provided, however, that no such public authority shall be required to expend any funds for such purposes in contravention of its trust indentures.