How is international trade affecting British Airways?

Answer 1

In so far as customers of BA can not get their flights 'imported' by container from China, not at all :-)

Perhaps you mean opportunities for additional Cargo carrying ??

In which case, I expect the main effect would be 'positive' = assuming they do as a lot of other airlines i.e. 'bulk out' under booked / under capacity flights with cargo containers (in place of hold luggage).