Regional slots have to maintain their regional status
Eg a SAAB CFS slot can be transferred to a 737 to CFS but not to a 737 to BNE
Interestingly if REX wanted to run a SAAB to BNE instead of CFS, they would not be permitted to transfer the slot
If REX wanted to get creative
They could run
SYD-CFS-BNE on a 737 using a regional slot