Not exactly from NCB, but you will get very good and frequent transport options from Cooch Behar town. First take a NBSTC bus or shared auto or taxi from New Cooch Behar to Cooch Behar NBSTC bust stand. Then take any bus (both private and NBSTC) to Alipurduar from the same place. Also, shared jeeps and taxis are available. Both buses and jeeps are very frequent from Coochbehar to Alipurduar. Once you reach Alipurduar, you can take any shared auto to Alipurduar Junction.