Tex. Utilities Code § 60.165

Except as prescribed in Chapters 61, 62, and 63, the commission may not adopt any rule or order that would prescribe for any local exchange company any affiliate rule, including any accounting rule, any cost allocation rule, or any structural separation rule, that is more burdensome than federal law or applicable rules or orders of the Federal Communications Commission. Notwithstanding any other provision in this title, the commission may not attribute or impute to a local exchange company a price discount offered by an affiliate of the local exchange company to the affiliate's customers. This section does not limit the authority of the commission to consider a complaint brought under Subchapter A, Chapter 52, Section 53.003, or this chapter.