The railway operating any spur track on any public street or property hereafter constructed in the City and County shall, upon demand of the person, firm or corporation for the use or benefit of which such spur track is operated, place upon such spur track the freight cars of any railway which has, in this City and County, track connection with the operating railway; such cars so placed to be used for the receipt and delivery of freight in carloads only. And the operating railway shall receive and deliver the cars of the connecting railway over, at and upon such connecting track in the performance of such switching services for such persons, firms or corporations and such railway shall perform such service without undue delay or discrimination. The operating railway shall perform such service for the same charge or rate that it charges for corresponding service for its own cars upon the spur track for like purpose. The provisions of this Section shall apply only to such portions of such spur tracks as are not constructed, maintained or operated upon or across private land, and no permit for a spur track shall hereafter be granted which does not specifically contain the provisions and conditions of this Section. Any provisions of this Section in conflict with state and federal laws shall not apply.