CA Pub Util Code Section 2117

(a)

Whenever a written notice to appear has been mailed to the owner of a passenger stage, an exact and legible duplicate copy of the notice, when filed with the magistrate in lieu of a verified complaint, is a complaint to which the defendant may plead guilty.

(b)

If, however, the defendant fails to appear, does not deposit bail, or pleads other than guilty to the offense charged, a complaint shall be filed which conforms to Chapter 2 (commencing with Section 948) of Title 5 of Part 2 of the Penal Code and which shall be deemed to be an original complaint, and thereafter the proceeding shall be held as provided by law, except that the defendant may, by an agreement in writing, subscribed by the defendant and filed with the court, waive the filing of a verified complaint and elect that the prosecution may proceed upon a written notice to appear.