Tex. Utilities Code § 40.053

(a) If a municipally owned utility chooses to participate in customer choice, after that choice all retail customers served by the municipally owned utility within the certificated retail service area of the municipally owned utility shall have the right of customer choice consistent with the provisions of this chapter, and the municipally owned utility shall provide open access for retail service.

(b) Notwithstanding Section 39.107, the metering function may not be deemed a competitive service for customers of the municipally owned utility within that service area and may, at the option of the municipally owned utility, continue to be offered by the municipally owned utility as sole provider.

(c) On its initiation of customer choice, a municipally owned utility may designate itself or one or more other entities as the provider or providers of last resort for customers within the municipally owned utility's certificated service area as that area existed on the date of the utility's initiation of customer choice. The municipally owned utility shall fulfill the role of default provider of last resort in the event no other entity is available to act in that capacity if the municipally owned utility continues to sell electric energy to retail customers after the initiation of customer choice. The municipally owned utility may delegate the authority to designate the provider or providers of last resort to the commission.

(d) If a customer is unable to obtain service from a retail electric provider or a municipally owned utility or electric cooperative offering customer choice, on request by the customer, the applicable provider of last resort shall offer the customer the standard retail service package for the appropriate customer class, with no interruption of service, at a fixed, nondiscountable rate that is at least sufficient to cover the reasonable costs of providing that service, as approved by the governing body of the municipally owned utility that has the authority to set rates. If a provider of last resort is designated by the commission, the commission may set the rate each provider of last resort may charge.

(e) The governing body of a municipally owned utility may establish the procedures and criteria for designating a provider of last resort and may redesignate a provider of last resort according to a schedule it considers appropriate. If the municipally owned utility delegates authority to the commission under Subsection (c), the commission is not required to comply with procedures or criteria adopted by the municipally owned utility.