The Australian Competition Tribunal has ruled that FTSE 100 mining company Rio Tinto's Hamersley and Robe rail network should not be opened up to other users.The move, announced on Monday morning, retains Rio Tinto's exclusive and unlimited use of the the railway lines.Paul Shannon, Rio Tinto Iron Ore Acting Chief Executive, said: "This is great news. Rio Tinto runs a highly efficient railway that is fully integrated with our port and mine operations. "This would be severely hindered if third parties were allowed to run trains on our rail network, not to mention the knock-on negative effect on the Western Australian and national economies from creating such inefficiencies."MF