The Board shall, for a class of rail carriers providing transportation subject to its jurisdiction under this part, prescribe, and change when necessary, those classes of property for which depreciation charges may be included under operating expenses and a rate of depreciation that may be charged to a class of property. The Board may classify those rail carriers for purposes of this section. A rail carrier for whom depreciation charges and rates of depreciation are in effect under this section for any class of property may not—