Hi
The reason for the MAN-MBA stopping in BSL is that the main tour operator is swiss based. It operats flights out of the UK, France, Switzerland, Germany and Austria. The operation from MAN as a stand alone is not big enough so a stop is required. In the past before the events in Kenya this flight used to stop in LGW.
The tour operator used to have its own A/C and airline African Safari Airways using a colourful DC8, then DC10 and finally A310. It ceased operations.