The longhorn was a hybrid meant to have better heat resistance and drought tolerance than the available shorthorns.
Brangus, a mix of Indian Brahma and Angus was another attempt to get a drought and heat tolerant stock.
Both of those have had some success.
All have which have paled before the genius of the Black Angus Marketing Board to create demand at the retail level. Which is a touch hilarious as there's no way to tell in the butcher's case what breed of stock a given steak is from. Not even primals will much tell you, either. Until you get to the whole side will you have enough anatomy to tell. Even then, "Black Angus" is really a Herford cross with Limosene, and really only refers to hide color. If you are raising beeves for profit, you really want them to all be of about a same size for the same requirements in water, grazing/feed, etc.
Now, a Cape Buff does not add that much to most beef cattle; and is probably a subtraction in dairy cattle (placid is a good characteristic in dairy stock, that, and fertility). Dairy production in dry environments is better met through goats or sheep than bovines.
Further, there has been some domestication of "Cape" stock, as water buffalo are one of the most common cattle stocks around the world. Water buffalo in Parma give us the milk for the eponymous cheese.
Water buffalo can make for good game stock, as the feral and wild versions are wily and tricky to harvest, with Capes being first on that list.