Tex. Transportation Code § 370.186

(a) Except as provided by Subsection (c), an authority may not construct, maintain, or operate a turnpike or toll project in an area having a governmental entity established under Chapter 284 or 366 unless the governmental entity and the authority enter into a written agreement specifying the terms and conditions under which the project shall be undertaken. An authority may not construct, maintain, or operate a transportation project that another governmental entity has determined to be a project under Chapter 451, 452, or 460 unless the governmental entity and the authority enter into a written agreement specifying the terms and conditions under which the project shall be undertaken.

(b) An authority may not receive or be paid revenue derived by another governmental entity operating under Chapter 284, 366, 451, 452, or 460 unless the governmental entity and the authority enter into a written agreement specifying the terms and conditions under which the revenue shall be received by or paid to the authority.

(c) Subsection (a) does not apply to a turnpike or toll project located in a county in which a regional tollway authority has transferred under Section 366.036 or 366.172:

(1) all turnpike projects of the regional tollway authority that are located in the county; and

(2) all work product developed by the regional tollway authority in determining the feasibility of the construction, improvement, extension, or expansion of a turnpike project to be located in the county.

(d) An authority may not construct, maintain, or operate a passenger rail facility within the boundaries of an intermunicipal commuter rail district created under former Article 6550c-1, Vernon's Texas Civil Statutes, as those boundaries existed on September 1, 2005, unless the district and the authority enter into a written agreement specifying the terms and conditions under which the project will be undertaken.