I should clarify: I think it was in 1987.
This is conjecture, and I'm always hesitant to get into that realm, but I suspect that it has something to do with the financial implications, obviously.
One of the standards is that, effectively the railway has to be made whole, and it's pretty hard to arrive at that resolution, first and foremost. Obviously, we can't speak definitively as to why it hasn't been used, but I suspect that's probably it.