(1) If a tariff is filed on statutory notice cancelling another tariff and after such filing a supplement to the tariff to be so cancelled should be issued effective prior to the general effective date of such new tariff, rates in such supplement could not continue in effect for the 30 days required by law because the cancellation of the former tariff also cancels supplements to it. In such a case, and confined to additions or to changes in rates or provisions which were brought forward in the new tariff without change, the provisions of ARM 38.3.2807 need not be observed as to the old tariff, and a supplement making the same changes in or additions to both tariffs may be issued as supplements both to the tariff in effect and to the tariff which will effect such cancellation, and be given both PSC numbers. In other words, such issue must be a supplement both to the old and the new tariffs and copies must be posted and filed accordingly. Only one such supplement may be in effect at any time.
(2) Rates or provisions which have been established in an old tariff and reproduced or reissued in a new tariff may be changed upon lawful notice by supplement to the new tariff, effective not earlier than the general effective date of the new tariff, by showing in the following manner in connection with the changed rates or provisions that the rates or provisions changed thereby have been in effect 30 days or more, in the former issue. Example: "Item 40-A cancels item 40.Item 40 effective , brought forward without change from Item No. of PSC No. (former issue) ."
(3) New rates or provisions which do not change rates or provisions in either the old or new tariff may be established upon lawful notice by supplement to the new tariff, effective not earlier than the general effective date of the new tariff, by showing in the following manner, in connection with the new rates or provisions that the rates or provisions previously applicable have been in effect 30 days or more in a former issue. Example: "Addition. Changes class rates which became effective in PSC No. ."Unless the provisions of this paragraph are complied with no supplement to a tariff that is on file and not yet effective may be made effective within 30 days from the effective date of the tariff with out special permission.