One of the interesting things about R3 (if it happens) will be the impact on air fares ex-LHR. BA are focussing solely on the higher airport charges, believing that these will result in higher air fares. But it's more complex than that - the major increase in slots and capacity will massively increase competition, and the result is likely to be downward pressure on air fares. EasyJet have pointed this out in their submission to Davies, believing that (even on short haul) competition will outweigh the impact of higher airport charges.
Previous studies have consistently shown that yields ex-LHR are materially higher than at, say, LGW. This is only sustainable due to the current high barriers to entry at LHR, reflecting the shortage of slots. Otherwise competition would drive down yields (and increase efficiency of the incumbents).
That's really what BA is scared of - losing their premium yields that result from their dominant market position. And, of course, finally having to address the problem of their high cost base and inefficient ground operation. Expect strikes, especially if BA's preferred solution is to increase VY's presence at LHR.