Mont. Code § 69-3-307
Costs or expenses incurred by public utilities for advertising, transfers of funds without full and adequate consideration, contributions, donations, and gifts may not be treated as expenses deductible from income or from capital assets or in any other manner by the public service commission in setting or regulating rates that may be charged by the public utilities pursuant to this chapter. This section does not apply to advertising that encourages the conservation of energy or product safety or informs the public of the availability of alternative forms of energy or recommends usage at times of lower rates or lower demand. Furthermore, for communications public utilities, the provisions of this section do not apply to advertising that relates to special equipment that is available to aid persons with disabilities or to special services that are designed to protect the public health, welfare, and safety, to promote more efficient use of a communications system, or to promote increased use of regulated communications services.
§ 69-3-307, MCA