I've done this quest before so this one confuses me. I had to reload my quest several times because I knew exactly where I was going and wasted no time. The train timing would vary but finally I was able to get on the train without it taking off around me and disable the bomb. Each time I tried it the train blew up anyway.
The old guy on the radio will say in the SAME segment how the monorail was destroyed and then how an attempt was foiled by a civilian contractor....
... where does it all end??