Tex. Civ. Practice & Remedies Code Section 123.003
Defense

(a)

A switchboard operator or an officer, employee, or agent of a communication common carrier whose facilities are used in the transmission of a wire communication may intercept, disclose, or use a communication in the normal course of employment if engaged in an activity that is necessary to service or for the protection of the carrier’s rights or property. A communication common carrier may not use service observation or random monitoring except for mechanical or service quality control checks.

(b)

It is a defense to an action under Section 123.002 (Cause of Action) that an interception, disclosure, or use of a communication is permitted by this section.

(c)

A defendant must establish by a preponderance of the evidence a defense raised under this section.

Acts 1985, 69th Leg., ch. 959, Sec. 1, eff. Sept. 1, 1985.