Bangladesh's Road Transport and Highways Division (RTHD) has said direct bus service between Dhaka and Siliguri is very likely to begin this year, although the agreement on which the service would start is yet to be finalized.
 
Talking to Dhaka Tribune, a senior official of the division said they want to finalize a bilateral agreement with India to start the service this year.

Although the service will be operated between Dhaka and Siliguri, but convenient transports will also be available at Siliguri for Bangladeshi nationals to travel to Gangtok and Darjeeling, two popular tourist places in India, via the route.

https://www.dhakatribune.com/bangladesh/2021/01/14/dhaka-siliguri-direct-bus-service-likely-to-start-this-year