Pub. Util. Code, § 1001.5

(a) The commission shall exempt the construction of any line, plant, or system, or extension thereof, located outside the boundaries of the state from the requirements of Section 1001, upon the application of the public utility constructing that line, plant, or system, or extension thereof, if the public utility derives 75 percent or more of its operating revenues from outside the state, as recorded in the fiscal period immediately before the filing of the application, unless the commission determines that the public interest requires that the construction should not be exempt from Section 1001.

(b) Except as provided in subdivision (c), the commission shall make the determination denying the exemption, as specified in subdivision (a), within 90 days after the public utility files the application for exemption with the commission. If the commission fails to make this determination within that 90-day period, the construction of that line, plant, or system, or extension thereof, is exempt from the requirements of Section 1001.

(c) The commission and the public utility filing the application for exemption may, if both agree, extend the time period within which the commission is required to make the determination denying the exemption, for not more than an additional 60 days after the expiration of the 90-day period specified in subdivision (b).