Join Date: Aug 2011
Location: Barcelona, London, on a plane
Programs: IB+ Gold, TK E+, Hyatt Globalist, Marriott LTP, IHG Diamond
Posts: 14,182
HUACA
Upgrades using Avios are a published benefit of Iberia Plus for all members. (of course the IB website makes it nearly impossible to find relevant information these days...)
You need to be booked in one of the required fare buckets AND have award space available in the upgraded cabin.