FYI only, although it might possibly be useful as a tie-in storyline (then again, maybe not). One of the threads in the mod I'm working on is finding and stopping a caravan of Black Lotus being brought up from Calimsham for distribution in Athkatla, Beregost and Baldur's Gate. It's coming up the Trade Way to just north of Crimmor where it remains at a place called Cerendor Hold (new area) in the Cloudpeak Mountains, until it can be moved back down to Crimmor and shipped downriver to Athkatla. From Athkatla it is shipped up to Baldur's Gate.
That destined for Beregost continues across the Cloudpeaks by waggon.