Hope that you have read this: https://abn397.wordpress.com/2015/05/11/more-from-the-border-from-hell-1/
An update which shows a group from West Bengal visiting this area. This was uploaded earlier in 2019.
Commentary is in Bengali with English subtitles.
The narrator was not quite correct about the pre-partition Darjeeling Mail. In fact it took over 13 hours from Sealdah to the old Siliguri Jn (now Siliguri Town). And it did not go anywhere near Bangaon and Jessore. Here you can see its timetable in 1944:
In the next post, you will see more about current passenger services on the BR trains through Hili. Remember that it is dual BG/MG. More precisely, it was BG since the 1920s and MG has been added after 2000, to facilitate MG services from Dhaka across the Bangabandhu Bridge to destinations such as Dinajpur, Rangpur and Lalmonirhat which are (or were until recently) on MG lines from Parbatipur.