Depends on which retirement system you're paying into when you retire. If you quit the RR and got an "SSI job", then your RRB contributions are rolled into your SSI pension. If you retire on an "RRB job", then your SSI contributions are rolled into your RRB pension. If you lost your RRB job through no fault of your own (like because of a merger); tried to find other RR employment and failed because of it causing great hardship (i.e. not being able to afford to move); and then notified the RRB that the only employment you could find is a non-RRB job, the RRB has been known to "deem a current connection" in this situation when you retire, making you eligible for an RRB pension (don't forget the 60-30 thing, and that with less than either, it will be a reduced pension). It can get quite complicated.