I know Boeing (not sure about others) issues the same reg #, and in this case and N number for the United States for a/c pre-delivery. These numbers are eventually replaced by the operator's reg #. Some examples:
Reg: N60659 (New 777-200LR, and a QF
747-400 from the early 1990s.)
Reg: N5014K (KLM 777-200, Aitalia 777-200, and 777-300 world tour a/c)
Reg: N6018N (KLM 777-200, China Southern 747-400F)
These regs are removed and then owner's reg is implemented. I think there is a pic in the database of an Independence Air A319 with the Airbus reg and FlyI reg on @ the same time.