I recently flew NCE-LHR-DXB on BA and then DXB-SYD on QF and wanted to make sure my luggage was checked all the way through to SYD. I even called BA ahead of time to check and they said that yes, as long as the connection at DXB is < 24 hours it won't be a problem. However, when checking in at NCE I was told that I would have to collect my luggage at DXB: they cannot check it through on the DXB-SYD segment, because that's still over 24 hours away. (The DXB-SYD flight departed exactly 24 hours after the NCE-LHR flight and check-in was, obviously, before that.)

On the way back I traveled on *A instead. SYD-BKK-FRA on TG and FRA-NCE on LH and it was not a problem. The FRA-NCE flight departed > 38 hours after the SYD-BKK one and the luggage still got checked through all the way to NCE.

So clearly this is not a universal rule. Is it a OW rule? Or a BA rule? Or did I just get a check-in agent who didn't know what they were talking about?

By the way, for anyone else going through this: I didn't actually have to exit at DXB and collect the luggage. The agent at the Emirates check-in desk who issued my BP also "re-tagged" my luggage in the system, so it presumably got collected from the carousel and loaded onto the DXB-SYD flight. I was a bit concerned, because he wouldn't give me a new luggage receipt showing "SYD", but it arrived in SYD just fine.