Minn. Stat. § 237.21: VALUATION OF TELEPHONE PROPERTY.

In determining the value of any telephone property for ratemaking purposes, no valuation shall be allowed upon the value of any franchise granted by the state or any municipality where no payment was or is being made to the state or municipality on account thereof. The requirement as to reasonableness of rates shall apply to each exchange unit as well as to telephone plants as a whole. Provided, that in the case of a company operating a telephone system consisting of more than one exchange in the state, reasonableness of rates, as measured by earnings, shall be determined by a reasonable return from the total operations of the system within the state rather than by the return from individual exchanges or services. No telephone rates or charges shall be allowed or approved by the commission under any circumstances, which are inadequate and which are intended to or naturally tend to destroy competition or produce a monopoly in telephone service in the locality affected.