District Attorney, authority for 424th

What is the statutory basis of the authority for the District Attorney elected in the 33rd Judicial District to also serve the 424th Judicial District?

At the outset of the bill drafting to create the new district (which bill ultimately became SB 1189) I had drafted language to piggy-back the D.A. onto the 424th but discovered that the Government Code already provided for that. New districts are now created under the "Judicial Districts Act of 1969" and the applicable provisions are as follows:

 Subtitle A. Courts
  Chapter 24. District Courts
   Subchapter C. Judicial Districts Act of 1969

§ 24.301. Application of Subchapter
Except as otherwise indicated by the context, this subchapter applies only to judicial districts listed in this subchapter.

§ 24.308. Court Officers
The prosecuting attorney, the sheriff, the district clerk, the bailiffs, and the other officers serving the other district courts of the county shall serve in their respective capacities for the courts listed in this subchapter.

§ 24.309. Jurisdiction
Each court listed in this subchapter has the jurisdiction provided by the constitution and the general laws of this state for district courts.

 Section 15 of SB 1189 then provides as follows:

    SECTION 15.  (a)  Effective September 1, 2005, Subchapter C, 
Chapter 24, Government Code, is amended by adding Section 24.568 to 
read as follows:
LLANO, AND SAN SABA COUNTIES).  (a)  The 424th Judicial District is 
composed of Blanco, Burnet, Llano, and San Saba Counties.
    (b)  The jurisdiction of the 424th District Court is 
concurrent with the jurisdiction of the 33rd District Court.
    (c)  The 424th District Court has the same terms of court as 
the 33rd District Court.

 Thus the 424th is created under the Judicial Districts Act of 1969 and the District Attorney for the 33rd is automatically the D.A. for the 424th.  For this reason the Legislative Council declined to keep my explicit language in the final draft of the bill.