The Commission shall examine alternatives to the construction of a new transmission line in a service area, including the use of an existing transmission line of another company, if: the existing transmission line is convenient to the service area; or the use of the transmission line will best promote economic and efficient service to the public. In considering the use of an existing transmission line under subsection (a) of this section, the Commission need not consider whether the company that owns the line has a franchise in a service area.