I suppose that when Manx did the franchise thing with BA at the same time that a few of its aircraft were operating flights for a close rival - British Midland - it was only a matter of time before a conflict of interests occurred. I guess that's what we saw with the BA-coloured ATP doing BM's work on that likely single occasion. The perils of getting into bed with the opposition! This episode may or may not have prompted SMB to buy Business Air in order to have suitable regional aircraft on the lighter BM routes. BM were, by this time, also flying to Paris from Leeds and Edinburgh too.
To diverge slightly, before the DC9s were disposed of, one of them operated regularly between Leeds and Glasgow, probably before the Business Air Saabs came along. Some years later, Fokker 100s were used between Leeds and Glasgow, Edinburgh and Paris, before BM disposed of them and before the Embraers came along. I remember some very healthy passenger loads on all three services. How grand it would be if Eastern or Loganair (or even FlyBe II) could be similarly successful for Leeds. MAJA has been based at LBA, on and off, for most of her life but I wouldn't like to think any future domestic network would be built around her ilk. Better than nothing but not ideal nowadays.