Cal. Public Utilities Code § 1001

(a) A railroad corporation whose railroad is operated primarily by electricity, street railroad corporation, gas corporation, electrical corporation, telegraph corporation, telephone corporation, water corporation, or sewer system corporation shall not begin the construction of a street railroad, of a line, plant, or system, or of any extension thereof, without having first obtained from the commission a certificate that the present or future public convenience and necessity require or will require its construction. (b) The extension, expansion, upgrade, or other modification of an existing electrical transmission facility, including transmission lines and substations, does not require a certificate that the present or future public convenience and necessity requires or will require its construction. (c) This article does not require those corporations to secure that certificate for an extension within any city or city and county within which it has lawfully commenced operations, for an extension into territory either within or without a city or city and county contiguous to its street railroad, line, plant, or system, and not served by a public utility of like character, or for an extension within or to territory already served by it, necessary in the ordinary course of its business. If any public utility, in constructing or extending its line, plant, or system, interferes or is about to interfere with the operation of the line, plant, or system of any other public utility or of the water system of a public agency, already constructed, the commission, on complaint of the public utility or public agency claiming to be injuriously affected, may, after hearing, make an order and prescribe terms and conditions for the location of the lines, plants, or systems affected as to it may seem just and reasonable.