(a) Not earlier than the 61st day after the date the interim executive committee approves a service plan and tax rate, the interim executive committee shall:
(1) modify the approved service plan and tax rate only as necessary to conform to the nonparticipation of municipalities or unincorporated areas in the service plan and approve the modified service plan and tax rate; and
(2) notify the commissioners court of each county included in whole or in part within the initial boundaries of the authority of the interim executive committee's intention to call a confirmation election.
(b) A changed service plan and rate of tax must be approved by the governing body of a contiguous municipality creating a subregional authority. Subsection (a) does not apply to an authority created by a contiguous municipality.