Frank, I do understand what BA's public line is. However, within Waterside, there is a school of thought that a no-R3 scenario might be a better result for BA, despite the clear drawbacks you refer to. Obviously BA can't say this publicly, as it would be seen as being anti-competitive.
(BTW I think they would be mad to take this line - BA are sailing pretty close to the wind on the "market power" issues already).
Not privy to the goings-on at Waterside, but there's always some in an organisation taking a contrarian view. Hard to believe that it could be a
better result. Sounds more like someone putting a brave face on it.
Publicly, IAG appear to have already come to terms with the fact that LHR won't get a third rwy, Willie Walsh has stated this on numerous occasions, and the attempted EI acquisition may be partly related to this fact.
Whether IAG really believes this or not is a moot point, but clearly no expansion at LHR is bad for the whole UK economy, not just for BA/IAG.