California Code, Streets and Highways Code - SHC § 1463

Any permit issued to a public agency or a public utility having lawful authority to occupy the highways shall contain a provision that in the event the future improvement of the highway necessitates the relocation of such encroachment the permittee will relocate the same at his sole expense.  In said event the road commissioner shall serve on the permittee his written demand specifying the place of relocation, and specifying a reasonable time within which the work of relocation must be commenced.  The permittee must commence such relocation within the time specified in said demand and thereafter diligently prosecute the same to completion.

All permits other than those issued to public agencies or a public utility having lawful authority to occupy the highways are revocable on five days' notice and the encroachment must be removed or relocated as may be specified by the road commissioner in the notice revoking the permit and within a reasonable time specified by the road commissioner unless the permit provides a specified time.

Public utilities may be required, within a reasonable time, to relocate such of their facilities as interfere with an enlarged public use of the highway, except in those cases where the enlarged use of the highway involves a state freeway.