The November 1954 edition of The Railway Magazine reported that, “An improved type of steam-heating tender for electric main-line trains has been brought into use on the Cape Western and Natal systems of South African Railways. The new tenders are fitted with automatic oil-burning generators and are stated to be both cleaner and more effective than the former coal-burning type."
Historically, passenger carriages in South Africa were heated using steam heating systems powered by steam locomotives, or later via steam generators in diesel/electric locomotives. These systems supplied steam through pipes to heaters within the coaches. Other than the short piece in The Railway Magazine, I have been unable to find any reference to the need for SHGs with Class 4E locomotives.