Cal. Pub. Util. Code § 1407
If any owner or claimant named in the petition resides out of the State or has departed from the State or cannot after due diligence be found within the State, or conceals himself to avoid service, or is a corporation having no managing or business agent, cashier or secretary or other officer upon whom summons may be served, who, after due diligence, can be found within the State, and the fact appears by affidavit to the satisfaction of the commission, and it also appears by such affidavit or by the petition that a cause of action exists against the owner or claimant on whom the service is to be made or that he is a necessary or proper party to the proceeding, the commission shall make an order that the service be made on such owner or claimant by publication of the commission's order to show cause. The order shall direct that the publication be made in a newspaper designated by the commission as likely to give notice to the person to be served, and for such time as the commission finds to be reasonable, at least once a week, but publication against an owner or claimant residing out of the State or absent therefrom shall not be less than two months. If the address of any owner or claimant, as stated in the petition, is out of the State, the secretary of the commission shall, within 15 days after the making and filing of the order to show cause, deposit or cause to be deposited a copy of that order, certified under the seal of the commission, with a copy of the petition attached thereto, in the United States mail, enclosed in a sealed envelope, registered, with postage prepaid, addressed to such owner or claimant at the address specified in the petition. When publication is ordered, personal service of a copy of the order to show cause and of the petition out of the State is equivalent to publication and deposit in the United States mail.
Ca. Pub. Util. Code § 1407