Any operator who constructs, operates or enlarges a roadway pursuant to this chapter shall secure and maintain a policy or policies of public liability insurance in form and amount satisfactory to the Commission and sufficient to insure coverage of tort liability to the public and employees, and to enable the continued operation of the roadway. Proofs of coverage and copies of policies shall be filed with the Commission. Nothing in this chapter shall be construed as or deemed a waiver of the sovereign immunity of the Commonwealth with respect to its participation or approval of all or any part of the roadway application or operation, including but not limited to interconnection of the roadway with the state highway system. Counties, cities and towns through which a roadway passes shall possess sovereign immunity with respect to roadway construction and operation.