California Code, Public Utilities Code - PUC § 8026

No person shall run, place, erect, or maintain any wire or cable used to conduct electricity, on any pole, or any crossarm, bracket, or other appliance attached to such pole, within a distance of 13 inches from the center line of the pole.

This section does not apply to signal wires or cables which are attached to a pole to which is attached no wire or cable other than signal wires or cables, except within the corporate limits of a city, nor shall this section apply to such wires or cables where they are placed vertically on poles, nor to bridle or jumper wires on any pole which are attached to signal wires on the same pole, nor to any aerial cable, as between such cable and any pole on which it originates or terminates.

Telephone toll lines may be exempt from the provisions of this section if proper evidence introduced before the commission proves to the satisfaction of the commission, that compliance would seriously interfere with long distance telephone transmission.

This section does not apply to wires run from lead wires to arc or incandescent lamps nor to transformers placed upon poles, nor to any wire or cable where it is attached to the top of a pole, as between it and the pole, nor to any aerial cable containing signal wires where the cable is attached to a pole on which no other wires or cables than wires continuing from the cable are maintained if electric light or power wires or cables are not maintained on the same side of the street or highway on which the aerial cable is placed.