The whole point of IAG is to maximise the profitability of IAG assets across the wider IAG group. Each IAG business has to have a good case to use those assets or a new home could be found. Like the A320NEOs for BA that will be going to Iberia unless BA get short haul profitability and efficiency back on target.
Is it a "breach of trust"? You'd be on firmer ground if it were "breach of contract" perhaps. Aren't TAP also taking new A330s instead of A350s, which is a step up in terms of range, capacity and performance that they won't be close to getting the most out of. Of course it may be sabre rattling to help EI management drive changes. It way also be untrue
