In my rules NCM is simultaneous with Combat Movement; there is no reinforcing areas you just captured in any circumstances.
Therefore, you can only rail units into territories you’ve held since your last turn, representing the problems of converting track gauges and so forth. You still have to build your attack in stages, giving the enemy the chance to counter-rail his own forces to that front, or to disrupt such movement by attacking vulnerable links in the chain of territories on your network.
If the Axis allows the Allies to move a large force from Cape Town to Moscow in one move they really deserve to get screwed.