55% true - IB own 45% of Vueling, and there is in fact a VY flight from Orly to Fiumicino... you can use Avios from an Iberia Plus account to buy VY flights, and this would be a Reward Flight Saver for 7,500 Avios one way.

Now if the OP can let us know how he is holding his Avios, someone might be able to explain the trick of shuffling them, which I think you have to do from BAEC to avios.com then on to IB.