Originally Posted by
Andriyko
In this specific case (BA*YV flight), policy does not seem to allow rebooking via MAD on IB, if I am interpreting the rules correctly. IB flights can be re-booked if they are part of the original ticket where a disruption occurred, but they cannot be added as a rebooking option.
Even if the policy does not allow it, EU261 mandates at earliest convenience and the airline may not preclude perfectly available and sensible alternatives. In reality if BA flat refuses, OP can rebook themselves on the desired flights and claim this back from BA or VY as the case may be. VY does have well publicised form for ignoring EU261 so be prepared to go to MCOL.