It's almost impossible to cross-charge baggage repatriation across airlines and, in my experience, I haven't actually seen it happen. There's just too many variables to ascertain that bag X was short-shipped because of airline A and not airline B (or by the airport whose infrastructure was used).

In those instances where two airlines are finding repeated problems in passing bags then it's more efficient to set up a working group with the local airport to get to the root cause of the issue, rather than trying to cross-charge one another. There were similar working groups between AA and BA at LHR, with HAL providing data and support (there one of the main problems was multi-reads), again between AA and BA at ORD (there the airport wasn't that involved, though the crumbling infrastructure at O'Hare was definitely to be blamed) and between WestJet and BA at YYZ, which led to some changes in the way bags were re-screened at Pearson.

Anyhow, back when the interline bag ban came into effect the grapevine was saying that it was being introduced to clamp down on revenue dilution, when people were inventing all sorts of weird and wonderful itineraries with self-connections to shave off costs. Qatar Airways was specifically mentioned because of their dumping on routes to Indochina/Far East from Northern Europe. Again, that was 'water cooler chatter', I didn't see anything official or any data to that extent.