IATA???
Who are they???
Facetious, I know, but IATA has never, in fact, had "rules" - they were never more than "agreements" and these IATA "agreements" are now virtually dead!!! The plethora of "no-frills" airlines who refuse to have any part of IATA are to blame for this, and the decision of the UK and US governments to allow these cowboys to operate outside IATA have ensured its slow death! I believe IATA will no longer exist once "Open Skies" goes ahead (and Willie Walsh believes he will negotiate the "Open Skies" agreement successfully within eighteen months - for Gatwick's sake, I hope he fails!!!)
FYI, the decision whether or not to interline baggage is entirely at the airline's discretion. Whilst the decision might not benefit BA itself, our senior managers are committed to reducing the £25 billion annually, across the industry, spent reuniting passengers with their baggage when said baggage had absolutey no hope of making connections!!!