I am trying to work out the 14 destinations now added as codeshares but I got to 16, 2 of which are not in SA. I imagine they will want to add Zimbabwe locations once that goes through the regulatory hurdles, though BA have a codeshare on Qatar for HRE.

BFN - Bloemfontain
DUR - Durban
ELS - East London
GRJ - George
HDS - Hoedspruit
KIM - Kimberley
PLZ - Port Elizabeth
PTG - Polokwane, also known as Pietersburg
PZB - Pietermaritzburg
RCB - Richards Bay
SIS - Sishen
SZK - Skukuza (Kruger National Park, a particularly beautiful airport)
UTN - Upington (a diversion airport, with a massive runway of 4,900 metres, 1,000 metres longer than LHR. I wonder if BA's A380 can divert there?)
UTT - Mthatha formerly Umtata.
WDH - Windhoek, Namibia
WVB - Walvis Bay, Namibia

These codeshares are only on BA combinations, you cannot book a say CPT - DUR as a separate booking under BA flight numbers, only 4Z prime.