Are these units any relation to the former BR class 302 electric units? (for a photo: http://br-multiple-units.tripod.com/class302/id2.html ) That's what the front end put me in mind of when I first saw it.
I really don't know. The commuters have had that "face" ever since I can remember, from the wooden motor coaches with hinged doors that I rode on as a kid in the 50s and early 60s. (See for a side-on example) It's very likely that the design was copied from a British model, since the first SA commuter trains were probably British built anyway. About that same time (late 50s, early 60s) the all steel commuters started making their appearance, and the motor coaches (and unmotorised end coaches) have stuck with the same basic cab design all the time.