The similarity between the CSARV and the SAMCC was that they were both staffed largely by railwaymen and the SAMCC badge was based on the CSARV badge which in turn had been based on the old Boer Republic NZASM Railways badge.
See attached photo of SAMCC badge in my collection.
Info below sourced from
http://orangemarmtrading.com/SA_Railway_History.html will help explain this situation a little better, I hope:
1902 - Central South African Railways. The Imperial Military Railways proceeded to assume control of all lines in the Transvaal and Orange River Colony, thereby also absorbing the NZASM, and it eventually became the Central South African Railways (CSAR), under the control of Lieutenant-Colonel Sir Percy Girouard.
1916 - South African Railways and Harbours. The Union of South Africa was established on 31 May 1910, consisting of the four former colonies, the Cape of Good Hope, Natal, Orange River and Transvaal. As a self-governing state of the British Empire, the Union remained under the formal rule of the British crown, represented in South Africa by a Governor-General. All railways in South Africa finally became a unified state-owned railway system in 1916 when the Central South African Railways, the Cape Government Railways and the Natal Government Railways were all merged by an Act of Parliament. Thus was born the South African Railways and Harbours (SAR&H). Later, when commercial aviation developed, the South African Airways also became a part of this huge land, sea and air transport system.
In WW2 the Railways and Harbour Brigade once again based their badge on the "winged loco wheel".