California Code, Revenue and Taxation Code - RTC § 723.1

Operating nonunitary properties are those that the assessee and its regulatory agency consider to be operating as a unit, but the board considers not part of the unit in the primary function of the assessee.This section does not apply to state-assessed property of regulated railway companies. In the case of regulated railway companies, there shall be only two classifications of property for purposes of this code, unitary and nonunitary.