This is one of our fantasy about electricity. That if we supply the high voltage current to a track in Mumbai CST, peoples standing on the track in New Delhi [~1400 km far] will get a shock?
No, Current always chooses the shortest path [rather a resistance-free path] in the circuit before to be grounded.
Since the ground is much nearer than New Delhi that too with much less resistance path, the maximum distance traveled by current will be just 17.2 cm [i.e the depth of rail] and not 1400 km [length of rail]. It shall be grounded in no time. You will simply end up with ‘earthing’.
But, Sleeper and ballast crabs are generally hard core insulators. So in this case, the current will find the nearest grounding spots.
which are available at every 100, 300, 500 or 1000 meters interval with a special code of practice for earthing 25kV like this:
Or, manually [for inspection] it can be done anywhere by clippers as:
and it will be earthed.
Let us assume there are not such earthing points available, and the sleepers to are insulators; even then it is practically impossible. You will require astronomical high amperes of current [do also consider the huge loss] to circulate it through the whole railway network.