This is cobblers
BA will interline on any airline as long as they have an interline agreement in place.
However to interline outside of oneworld you need to have your flights all on one ticket, so for example GLA-LHR on BA and LHR-DXB on Ek will be fine on one ticket but not two.
The only difference to this is other oneworld airlines where BA will interline on separate tickets.
cs