leaking may coz by many reason,
1. some because waterproofing problem, mean the upper unit waterproofing had problem, then only the water is leak from the upper floor to lower ceiling, then upper floor need to pay.
2. If upper water pipe leaking and wet until lower unit, then upper floor pay.
3. If lower floor pipe leaking, of coz that usually will not effected upper floor, so lower floor pay.

In general, check who's leaking, then who pay. That is possible to check where the leaking from.

If what u say it 100% correct, then just to make sure the lower floor ceiling pipe is belong to upper floor or lower floor, as long as had know the pipe is belong to which floor, then that floor will be pay for it. However, sometime that will still be challenge by why the pipe is leak, for example, if upper floor change floor tiles and hack too deep until break the pipe. or lower floor make a drill to ceiling for reason then make the pipe leak.

As per what I know is the condo management have to be a middle party, they need to check on the situation and find out who's piping is leaking. If the management side report is not accept by lower or upper level, then challenge it to the court then, at that time, both of them will need to spend lot of money for lawyer and specialist to check on the place with report, so at the end, they have their own choice to choose what way to settle.