Mo. Rev. Stat. § 392.420
The commission is authorized, in connection with the issuance or modification of a certificate of interexchange or local exchange service authority or the modification of a certificate of public convenience and necessity for interexchange or local exchange telecommunications service, to entertain a petition to suspend or modify the application of its rules or the application of any statutory provision contained in sections 392.200 to 392.340 if such waiver or modification is otherwise consistent with the other provisions of sections 392.361 to 392.520 and the purposes of this chapter. In the case of an application for certificate of service authority to provide basic local telecommunications service filed by an alternative local exchange telecommunications company, and for all existing alternative local exchange telecommunications companies, the commission shall waive, at a minimum, the application and enforcement of its quality of service and billing standards rules, as well as the provisions of subsection 2 of section 392.210, subsection 1 of section 392.240, subsections 1 and 4 of section 392.245, and sections 392.270, 392.280, 392.290, 392.300, 392.310, 392.320, 392.330, and 392.340. Notwithstanding any other provision of law in this chapter and chapter 386, where an alternative local exchange telecommunications company is authorized to provide local exchange telecommunications services in an incumbent local exchange telecommunications company's authorized service area, the incumbent local exchange telecommunications company may opt into all or some of the above-listed statutory and commission rule waivers by filing a notice of election with the commission that specifies which waivers are elected. In addition, where an interconnected voice over internet protocol service provider is registered to provide service in an incumbent local exchange telecommunications company's authorized service area under section 392.550, the incumbent local exchange telecommunications company may opt into all or some of the above-listed statutory and commission rule waivers by filing a notice of election with the commission that specifies which waivers are elected. The commission may reimpose its quality of service and billing standards rules, as applicable, on an incumbent local exchange telecommunications company but not on a company-granted competitive status under subdivision (7) of subsection 5 of section 392.245 in an exchange where there is no alternative local exchange telecommunications company or interconnected voice over internet protocol service provider that is certificated or registered to provide local voice service only upon a finding, following formal notice and hearing, that the incumbent local exchange telecommunications company has engaged in a pattern or practice of inadequate service. Prior to formal notice and hearing, the commission shall notify the incumbent local exchange telecommunications company of any deficiencies and provide such company an opportunity to remedy such deficiencies in a reasonable amount of time, but not less than sixty days. Should the incumbent local exchange telecommunications company remedy such deficiencies within a reasonable amount of time, the commission shall not reimpose its quality of service or billing standards on such company.
§ 392.420, RSMo