Tex. Gov't Code § 853.301
(a) The governing body of a participating municipality by ordinance may authorize the granting of prior service credit in the retirement system for service performed in a public hospital, utility, or other public facility currently operated by the municipality, during a time the facility was operated by a unit of government other than the municipality and before:
(b) A member eligible to receive credit under this section after an ordinance is adopted under Subsection (a) is one who was employed by the municipality at a public facility:
Acts 1981, 67th Leg., p. 1876, ch. 453, Sec. 1, eff. Sept. 1, 1981. Renumbered from Vernon's Ann.Civ.St. Title 110B, Sec. 63.301 and amended by Acts 1989, 71st Leg., ch. 179, Sec. 1, eff. Sept. 1, 1989.