I couldn't find anything online but I imagine the process would be similar. The stuff in your TSP would be yours to keep. If you got a civil service job you'd then get a civil service TSP. if you like you can combine them.And, mods, suggest a possible new thread, but does anyone know of what the implications are if one switches to BRS and intends on working with the Federal Government and want to buy into the FERS retirement (Am I even using the right terms? Can someone who has been there done that explain how this process even works?)
I imagine you could buy back your service time to put towards FERS time in service. If you did 20 you'd have to do the math to see if it'd be worth "buying back" into FERS (retire as an E-6 and then make GS-15 would probably make sense to get full time credit as a GS-15).