The Pennsylvania Turnpike Commission may not enter into a public-private transportation partnership agreement in the capacity of a proprietary public entity with respect to granting substantial oversight and control over the Turnpike Mainline to another entity unless specific authority is granted through an act of law passed by the General Assembly. However, this shall not restrict the Pennsylvania Turnpike Commission from entering into a public-private transportation partnership agreement under this chapter or under other statutes which does not involve granting substantial oversight and control over the Turnpike Mainline to another entity.