I seem to recall Boeing having a large parts store opposite SEA. Is it still there? It must be one of the I better places to need a part for a 777 in a hurray.
In the early days of Virgin Atlantic I had a colleague who knew someone who worked for B.Cal. engineering who did work for VS (so this is coming to you third hand) who said that BA engineering would not supply a part to VS but were happy to do so when it was requested for a B.Cal. aircraft. (Perhaps there was something in "Dirty Tricks".)
Hopefully aviation is now a mature industry so this doesn't happen now. Fingers crossed.