I've always thought that code-sharing means, in principium, ...sharing. Sharing capacity, revenue and costs in proportions set.
Now it seems all IB can do with code-shared flights is just selling tickets and BA retains the right to accept them or not, on the grounds that the particular flight is their metal. Ridiculous.
Whether UX has or don't have a standing agreement with BA is irrelevant as it was IB's ticket (as they accepted UX's FIM). And IB has all sorts of guaranteed payment agreements with BA, don't they?
I don't understand why IB didn't stand firm with BA.
Iberia's staff sending people with small children to another terminal to sort out problem created basically by Iberia (they issued a BP which wasn't honoured) is a shame, to say the least.