FlyerTalk Evangelist
Join Date: Aug 2011
Location: Barcelona, London, on a plane
Programs: BA Silver, TK E+, AA PP, Hyatt Globalist, Marriott LT Plat, Hilton Diamond
Posts: 13,048
I'm not sure you can even upgrade codeshares.
You definitely can't upgrade IB7XXX flights using Iberia Avios. On Iberia metal, you'd have to book Y, B, H class in Economy for IB upgrades.
On BA metal, you'd have to book PE and upgrade using Avios if you want to fly in Business. I'm not sure whether BAEC will let you upgrade a BA flight booked under a non-BA code.