Why only Retired Waste can it move by train if forward on cargo module, train cars and train line and network. the others in the same family (Fission product, Plutonium, Spent fuel and Spent MOX) if only on train cars, train line and network not on cargo module

Logical gues would be, you really dont want that to happen because of radioactivity.

If 1-4 trucks transporting plutonium already gives a -25% population growth, imagine a full train load.

Probably disabled because of radioactivity.