[Zach_the_Lizard]

In New York the signalling system on most lines is ancient. The L train has a CBTC signalling system and it has real time arrival information. The 1/2/3/ and 4/5/6 have had upgrades, though not to CBTC, to provide similar countdown clock functionality. The 7 train is undergoing work to install CBTC.

On other lines, my understanding is that the signalling system doesn't know which train occupies a block, just that a train occupies the block. Which block is occupied isn't sent to a central control center either.

So "there's a Brooklyn-bound train 2 stops away" is the best it can do, since it can know based on which side of the tracks the train is on where the train is going. It can't know the letter or number.