§ 15. Actions and proceedings against the commissioner or the state; intervention by commissioner in certain actions and proceedings. With regard to duties or liabilities arising out of this chapter, the state or the commissioner may be sued in the same manner as a private person. In any action or proceeding affecting any state project the commissioner shall be given notice thereof, and he shall take such steps in such action or proceeding as may be necessary to protect the public interest. If, in the opinion of the commissioner, it is necessary or desirable in the public interest, that he intervene in such action or proceeding he shall be permitted to do so as a matter of right. Whenever in connection with a state project under any instrument or law, a notice of default in writing is required to be served upon an authority or municipality before the institution of any action or proceeding, a copy of such notice shall be served upon the commissioner at least five days before commencement of the action or proceeding. No costs shall be awarded against the commissioner or the state in any such litigation.