(a) Book depreciation and amortization for ratemaking purposes shall be computed on a straight-line basis over the useful life expectancy of the item of property or facility in question.
(b) In any rate proceeding where items of plant, revenues, expenses, taxes, or reserves are shared by or are common to the service area in question and any other service area, these items shall be allocated to fairly and justly apportion them between the area in question and any other service area of the utility.
(c) In any rate proceeding involving a gas utility that engages in both utility and nonutility activities, all items of plant, revenues, expenses, taxes, and reserves shall be allocated to fairly and justly apportion them between the utility operations and the nonutility operations. No items of plant, revenues, expenses, taxes, or reserves allocable to nonutility operations shall be included in any figures used to arrive at any rate to be charged by a gas utility for utility service, unless clearly shown to be integral to utility operations.

Source Note: The provisions of this §7.5252 adopted to be effective July 29, 2002, 27 TexReg 6687