Last fall, inbound to Brazza, overhead and talking to Kinshasha Control, I counted 8 flights on frequency and nary a TCAS symbol. At FL100 and TCAS looking BELOW! No transponder, no TCAS, and the locals seem not to like transponders. Or cannot get them fixed.
That said, we had no problems with contacting various control agencies, not that it mattered, IMHO.
GF