(a) This section applies only to a district created by a municipality that has elected to be added to the territory of a regional transportation authority under Section 452.6025, Transportation Code.
(b) The board shall reduce the sales and use tax imposed for the benefit of the district to the highest rate that will not impair the imposition of the regional transportation authority's sales and use tax on or before the effective date of the addition of the municipality to the authority as determined by the executive committee of the regional transportation authority under Section 452.6025, Transportation Code.