BA has not bought a stake in Norwegian, “Brand Agnostic” IAG has.
If you look at Aer Lingus it has expanded with quite a lot of autonomy under IAG. It has kept partnerships with United and JetBlue and still hasn’t joined Oneworld or the AA/BA TATL JV.
An airline with a strong brand, particularly in regions where other IAG airlines are weak, is exactly what IAG wants and there’s
no way they would just kill it.
IAG’s modus operandi is quite transparent and they certainly don’t make life easy for BA.