Originally Posted by
JohnnyColombia
The link you quoted is a definition of 'Eligible' flights that includes flights that have an IB flight number where the aircraft travelled on is an Iberia aircraft (including franchises).
Air Nostrum
is an independent carrier which operates as a franchisee of Iberia Airlines and Binter Canarias.
So, if you're traveling on Air Nostrum operated flight with an IB flight number it is logical to conclude that it's an eligible flight.
Not sure I can see anything more specific on the BA website though.