BA has some great flights form IAD to LHR but due to anti trust, I can't earn TATL miles on my AA account.

I think it is time these anti trust concerns are re-looked at.

Star Alliance and Sky Team have great options from IAD TATL but for One World, you really only have Iberia now. I don't consider BA or AA "One World" for purposes of TATL since you can't earn miles on the other carrier.

From IAD you have Star Alliance or SKy Team:
United
LH
Air France
KLM
SAS

all of these are great TATL options. Where is the Anti Trust concern???