As a PTF they are fulltime. So any leave amassed from AUX service carries over to new job title.
There are times when amassed AL is paid out to the RCA carrier if there is a long period of service after a break of service on routes that earn AL/SL. Don't know how long it takes for a payout of AL leave in that example.
IE... RCA on long term hold down of a route. The Reg carrier returns to serve the route again. So they become an RCA again.