The A380 is a regular topic of discussion elsewhere, and that's a partial answer. More recently the RR issue with 787s - also discussed elsewhere - can impact LAX. What is certainly the case that if BA has to cancel say 3 to 5 departures from LHR (out of 350 departures per day, to add context) then yes LAX may well be targeted to a degree since BA can readily rebook people on to AA and / or via connections elsewhere with BA / AA / IB. Moreover if there is a cancel of the day, BA also can move traffic to Virgin / Delta on top, so lots of options. Whereas it can be a lot more complex for South Africa or Dubai or Middle East countries, the alternatives may be more difficult to see.

BCN gets more cancellations that LAX, by the way. See the FAQ for cancellations for daily reports.