Section 8. The corporation shall be liable in contract or in tort in the same manner as a private corporation. The directors, employees, officers and agents of the corporation shall not be liable as such on its contracts or for torts not committed or directly authorized by them. The property or funds of the corporation shall not be subject to attachment or to levy and sale on execution, but if the corporation refuses to pay a judgment entered against it in any court of competent jurisdiction, the superior court, sitting within and for the county in which the corporation is situated, may, by writ of mandamus, direct the treasurer of such agency to pay such judgment. The real estate of the corporation shall not be subject to liens under chapter two hundred fifty-four but the provisions of sections twenty-eight and twenty-nine of chapter one hundred forty-nine shall be applicable to any construction work by the corporation.