first off, how did you come across having four pregnant females at once? did you know for absolute certain that they were pregnant? second, if I were you I would get them to the vet ASAP, to make sure no one is ill, and there are no dead babies left inside anyone.
Third, I am sorry about your possible rehoming situation.. hopefully things can get sorted out. how many rats do you have in total right now? maybe the fact that no one had any babies was a good thing if this situation came up.. start looking for fosters or possible adopters now, just so that, if things do change and you can not keep your rats, they have somewhere safe lined up to stay. If everything works out, then hey! If I were a possible foster/adopter, I would be glad to know a bad situation was reversed and the kids got to stay with their mom