Technically, if the LDB info was hackable (in the clean sense of the word), then you could approximate locations.
For instance, if you know that a train is "on time", having left "Station A", "X" minutes ago and is now "Y" minutes from "Station B", which is "Z" miles from "Station A"...
...but GPS data is more accurate!
For instance, if you know that a train is "on time", having left "Station A", "X" minutes ago and is now "Y" minutes from "Station B", which is "Z" miles from "Station A"...
...but GPS data is more accurate!