Windhoek ATC was donated an old east German mobile military radar about 10 years ago. It never did work properly though.
Procedural controlling is practised here. Or maybe none....!
The aircraft transiting the TMA(C404) would have received a clearance to enter controlled airspace from the ATC at the departure aerodrome (Eros) and would then be on the same frequency as the B737 was which departed from FYWH.