Think I answered my own question (buried in the Iberia Spain site under baggage):

This allowance is applicable on all Iberia flights as well as those operated by Iberia Regional Air Nostrum. If you are travelling on a code share flight with a flight number that corresponds with either the IB-5000 or IB-7000 series, the regulations of the operating company concerning luggage allowance will apply.

Still trying to figure out if I will earn any mileage?