Here are extracts showing the timetable of the Calcutta-Siliguri route in 1953:
As you can see, the border line crossed between Chilhati and Haldibari stations.
Recent pictures of these stations:
Further south, the Radcliffe line crossed between Banpur and Darsana. Later Gede station was built closer to the border.
As we well know, the Maitri Express and some goods trains cross the Gede-Darsana border. Probably the Haldibari-Chilhati border will be used for goods trains only. In case you are wondering, there have been many attempts by Indian governments over the years to get Bangladesh to allow transit for Indian road vehicles and trains to cross Bangladesh to reach North Bengal and the Northeast. They do not seem to like the idea. In fact, tourist visas issued to Indians invariably mention that you must enter and leave from the same point if traveling by land e.g. if you enter at Benapole you have to leave at Benapole.
Anyway, there are some interesting stories connected with the Haldibari-Siliguri section, which I will take up next.