This railway is all but abandoned and it appears that way when travelling through the site. I only came across the railway by accident as I explain in the linked article: https://rogerfarnworth.wordpress.com/2018/08/01/bicester-military-railway Much of the site has been sold off. The northern half of Graven Hill Depot is now an estate of plots for self build homes! (https://www.gravenhill.co.uk)
Recently, I have been reading a book about the Bicester Military Railway which was published in 1992. It was published by the Oxford Publishing Company and is widely available to buy second-hand. It is worth a read. ... http://rogerfarnworth.com/2019/10/12/bicester-military-railway-book-review