Manono project does not need to transport 350 million tons a year, just 440Kt per year for 2Mtpa capacity, or up to 2Mt a year for 10Mtpa capacity.
Bear in mind, Sicomines is required to contribute USD$3 billion on building infrastructures in DRC. I believe still have over US$2B to spend. Hydropowder station and Road infrastructure (US$350M) are Free!