The uncoupling of Transnet's Freight Rail division was rejected by CE Brian Molefe, but was backed by the United Transport and Allied Trade Unions (Utatu).
Molefe pointed to the failure of similar international models. He said international experience was replete with examples of separating operations from the network's management and the infrastructure not producing the desired outcomes.
Molefe said capital investment was needed to restore the proper functioning of the freight-rail business after two decades of under-investment.
"Yes, the role of the private sector needs to be debated, but we need to ensure that we invest and maintain the infrastructure. Transnet is already engaged in fundraising initiatives," he said.
Utatu general secretary Steve Harris said: "You can't take infrastructure away from the company. The problem lies with the government. This government and the previous are liable for their failure to invest in infrastructure. You can't keep on maintaining," he said.
Harris said Transnet's problem was 30 years of not investing and training people. There used to be 3000 to 4000 technical trainees; now there were about 500.
"This is not about the fear of the job losses that we trade unionists are always branded with, but it's a clear and simple call of solving the problem through investment and training. Transnet is about to do that," he said.
Chris Hart, an economist at Investment Solutions, said: "Yes, the problem has been under-capitalisation. But the point is the current model is a failure.
"Opening it up to new investors could solve the problem of under-capitalisation. Yes, it will need an investor with deep pockets to participate, but with a good and attractive project, surely investors will be there."