My understanding of Judicial Review is that it is generally about procedure rather than the merits of the decision. That being the case I was surprised that this even went to JR (although I believe that NR may not initially have done everything it should have done). The law lays down the procedures that have to be gone through including an enquiry. During that process the arguments by all sides are heard as are the objections. At the end the inspector makes his report. It is then up to the Secretary of State to decide to grant the order or not or to grant with modification. He doesn't have go along with the inspectors views. If he decides to grant the merits of the order can't be questioned what can be questioned is whether or not the correct procedures were followed and whether or not the Secretary of State had the legal power to grant the order or elements within it. If not the judge on review could quash the order. However it is possible to go back and go through the whole procedure again this time doing everything properly and then the Secretary of State grant exactly the same order.
So far everything I have so far read suggests that the Marks arguments are about the merit of the Decision rather than procedure.
Absolutely this is my understanding too. And if they go through the process again then Marks option will be off the table as the land will be unavailable. As he has said he does not want the development stalled, he wants it stopped. He is gambling on both winning the case and Network Rail with its current finances giving up.