patlini, it's a terrific contribution. Thanks. Your work does not settle the question of precisely where the camel action is, but in combination with puddin's photo of the camels in Dori it limts the possibilities, which is an excellent thing.
I searched hard for photos of Dori, found few, and none had any camels.
At this point, Markoye is in the Sahel and would be the top choice from the camels' point of view. However, the knowledge that there are really camels in the Dori area is sufficient to make that my favorite since Dori is directly on the main northern route to Niger and from Markoye they have to take the unpaved road to Gorom-Gorom and then the paved road south to Dori, maybe 80km total, to get to Dori. From Dori teams would just go east and cross into Niger. This may not seem like much, but the extra 2 hours round-trip up to Markoye and back could be critical and I don't think World Race Productions would have designed it to take the extra distance and time.