CA Civ Proc Code Section 2025.310

(a)

A person may take, and any person other than the deponent may attend, a deposition by telephone or other remote electronic means.

(b)

The court may expressly provide that a nonparty deponent may appear at the deposition by telephone if it finds there is good cause and no prejudice to any party. A party deponent shall appear at the deposition in person and be in the presence of the deposition officer.

(c)

The procedures to implement this section shall be established by court order in the specific action or proceeding or by the California Rules of Court.