(a) The governing body of a municipality may adopt an ordinance to declare an area that is adjacent to the municipality and that meets the requirements of Subsection (b) to be a part of the municipality. The adoption of the ordinance creates an irrebuttable presumption that the area is a part of the municipality for all purposes. The presumption may not be contested for any cause after the effective date of the ordinance.
(b) An area qualifies for inclusion in a municipality under this section only if, on the date of the adoption of the ordinance:
(1) the records of the municipality indicate that the area has been a part of the municipality for at least the preceding 20 years;
(2) the municipality has provided municipal services, including police protection, to the area and has otherwise treated the area as a part of the municipality during the preceding 20 years;
(3) there has not been a final judicial determination during the preceding 20 years that the area is outside the boundaries of the municipality; and
(4) there is no pending lawsuit that challenges the inclusion of the area as part of the municipality.

(c) The date on which an area that is made a part of a municipality under this section is considered to be a part of the municipality is retroactive to the date on which the municipality began its continuous treatment of the area as part of the municipality. That date shall be used for all relevant purposes, including a determination of whether territory allegedly annexed by the municipality was adjacent to the municipality at the time of the purported annexation.