Looking at booking some flights through BA (have an eVoucher). I am trying to fly WTP/PE round-trip. For the way back, I can't tell if what I'm looking at booking is actually PE on IB or Economy. It's a BAXXXX code share flight, operated by IB (MAD-JFK). I have two different ways I've looked at booking it. One uses fare code S for that segment, the other fare code T. Are either of those actually booking into PE on IB?