(

a) The Legislature encourages all counties to utilize the procedure described in this chapter, but recognizes that it is not feasible for every county to establish its own programs. Accordingly, two or more counties may jointly establish programs pursuant to

Section of this code or

Article 1 (commencing with

Section 6500) of

Chapter of Division of Title of the Government Code or may furnish by contract the program services to residents of another county pursuant to

Section of this code. The board of supervisors of the county in which the program is located shall be responsible for assuring the integrity of the program as required pursuant to subdivision (

a) of

Section 11837.6. (

b) For the purpose of determining a person’s eligibility to participate in an approved program where the person’s county of residence establishes a program with another county or contracts for services pursuant to subdivision (a), the following eligibility requirements shall apply:

(1) Where two or more counties jointly establish a program pursuant to

Section of this code or

Article 1 (commencing with

Section 6500) of

Chapter of Division of Title of the Government Code, subdivision (

b) of

Section 11838.2 shall apply.

(2) Where a county contracts for program services from another county, only those residents alleged to have committed a violation of

Section or of the Vehicle Code on or after the date their county of residence executes a contract pursuant to subdivision (

a) to provide program services to their residents shall be eligible to participate in such approved program pursuant to

Section 11837.2. Counties which contract for services pursuant to subdivision (

a) of this

section shall notify the department not later than days following such action.