Bonds, notes or other evidences of indebtedness issued by the agency may be secured by a trust indenture or trust indentures by and between the agency and a corporate trustee, which may be any trust company or bank having the power of a trust company within or outside this Commonwealth. Such trust indenture may contain such provisions for protecting and enforcing the rights and remedies of the holders thereof, as may be reasonable and proper and not in violation of law, including covenants setting forth the duties of the agency in relation to the exercise of its statutory powers and the custody, safeguarding and application of all moneys. The agency may provide by such trust indenture for the payment of the proceeds of such obligations of the agency and the revenues to the trustee under such trust indenture or other depository, and for the method of disbursement thereof, with such safeguards and restrictions as the board of directors may determine. All expenses incurred in carrying out such trust indenture may be treated as part of the operating expenses of the agency. Such trust indenture may limit or abrogate the right of the holders of any bonds, notes or other obligations of the agency to appoint a trustee under this act or limit the rights, powers and duties of such trustee.