(If you're still looking...)
This photo from 1959 shows what's clearly a Whitcomb centercab. It appears identical to locomotives for the Bas Congo - Katanga railway, and closely related to those for Brazil's EF Sorocabana and the Portuguese Class 1300.
Thomas Kautzor's reports on Mali and Senegal suggest more. The BB500 series are given as "Alsthom 1955", the BB550 as "Alsthom 44t 1956". No pictures. The BB1100 built 1959-65 are described as "Alsthom AD12B". The BB1200 are later-model AD12B, the one seen in your link for 1979. The BB1100 would be the earlier version -- see, for example, this Tunisian example. These are standard French export models. The difference between the Portuguese 9000 (early) and 9020 (late). Or in Ethiopia.
Christian Derosier claims the blocky Henschel diesels are from 1963, but I suspect the 1983 quoted on the other pages is correct. (Similar-looking Henschel-EMDs in Sudan and Ghana are from the 1970s-80s.)
Ah, here's what I was looking for. A roster for the Dakar-Niger.
Full dieselisation of the AOF railroads took place between 1947 and
The 1960 roster includes 15 Alsthom-Sulzer boxcabs, 8 Sulzer endcabs of class BB400, 11 Alsthom BB500, 5 Alsthom BB600 (are these lower-powered versions of...?), 6 Alsthom BB1100, 6 Whitcomb CC1300, 4 diesel railcars. Note no BB550 -- were they acquired secondhand later?