I assume that the transfer will be 1:1.
Having had a quick look at the BA Exec Club redemption tables (and boy are they complicated with three defferent tabels depending on the combination of airlines you are flying) but it seems that their redemption levels are higher than LX's.
Would b a nice welcome gesture if we got more than 1 Exec Club miles for every Travel Club mile but I would be very surprised indeed if that were to happen.
Stephen