California Code, Government Code - GOV § 56427

The commission shall adopt, amend, or update spheres of influence after a public hearing called and held for that purpose.  At least 21 days prior to the date of that hearing, the executive officer shall give mailed notice of the hearing to each affected local agency or affected county, and to any interested party who has filed a written request for notice with the executive officer.  In addition, at least 21 days prior to the date of that hearing, the executive officer shall cause notice of the hearing to be published in accordance with Section 56153 in a newspaper of general circulation which is circulated within the territory affected by the sphere of influence proposed to be adopted.  The commission may continue from time to time any hearing called pursuant to this section.

At any hearing called and held pursuant to this section, the commission shall hear and consider oral or written testimony presented by any affected local agency or affected county or any interested person who wishes to appear.

This section shall only apply to spheres of influence adopted by the commission after January 1, 1975.