Tex. Loc. Gov't Code § 552.074

A certificate of special assessment issued under this subchapter, including a certificate issued under a joint proceeding under Section 552.072, is a legal and authorized investment for a bank, savings bank, trust company, savings and loan association, insurance company, sinking fund of a municipality, county, school district, or other political subdivision of this state, and for all other public funds of this state or an agency of this state.