Conn. Gen. Stat. § 13b-231

For the purpose of establishing tax exemption projects and determining the degree of compliance therewith, the Commissioner of Transportation may examine the accounts, books, and documents of each railroad for which he is preparing or has promulgated tax exemption projects, may inspect the transportation property of such railroad and the performance of maintenance, cleaning and rehabilitation work thereon, may hold investigations and hearings within or without the state, either separately or jointly with appropriate agencies of other jurisdictions, and shall have power to compel the attendance of witnesses and the production of accounts, books and documents by the issuance of a subpoena.