Cal. Pub. Util. Code § 1205

If any order of the commission provides for the payment of a portion of the cost of any such grade separation by a political subdivision without authorizing the assessment of all or any part thereof upon a benefited district, the legislative body of the political subdivision may at any time thereafter apply to the commission to have the order modified in accordance with any finding made by the legislative body, and the commission may thereupon make a new or modified order in the same manner as if such application had been made to it before the making of the order.