Have a look on the Secret Leeds Website forums, loads of stuff on there about the tunnels. Sure I've read topics on there, possibly some with photos too.
Its a great site in general about the history of Leeds, with various topics on transport/railways in Leeds from days gone by.
--- old post above --- --- new post below ---
Hope I'm alright posting links to other web forums, if not I'll PM you them later.
http://www.secretleeds.com/forum/Messages.aspx?ThreadID=379 This thread relates to the "Dark Arches" deep below the station. Nothing railway related, just culverts and rivers, still interesting mind, with lots of photos.
http://www.secretleeds.com/forum/Messages.aspx?ThreadID=153&StartAtMessage=25 This thread relates to the once public areas of Leeds station that are now restricted.
Im sure there's more threads on there if you look through it. As I said, Im not promoting the site (as far as I'm aware the site is funded by Leeds City Council), just pointing him in the direction of his answers.