Jeff posted a bit on here some years ago. He was doing some scent detection work (narcotics & explosives) with Basenjis if memory serves, and yes, he did off leash tracking with them as well. I believe he is a retired police K9 handler and has written quite a lot about tracking and trailing, including books on the subject. The interest in Basenjis for this work was probably because of their size and agility. In the end I don't know if he continued to pursue it.
I have an older book by Susan Coe that has a section on training the Basenji for the hunting field, by Major Al Braun. It has quite a few pictures, including a Basenji retrieving a duck from a pond. Back in the 1970s there were field trials for Basenjis in Minnesota, so there must have been a few people using them at that time. Too bad we have pretty much lost that interest in using the dog for hunting. Obviously there was a time when people managed to make partners of their Basenji and that these dogs could be trusted to work off leash.