Hand baggage only fare and Oneworld allowance
 

Does anyone know if for Iberia (and Iberia express) the One World benefits (hold baggage) apply when the most basic fare (hand baggage only) for economy is purchased. Also is this stated online somewhere? Asking because for AA and BA this is not the case and we get 0 hold bags.

Yes, you should get one free bag with IB.

https://www.iberia.com/us/luggage/al...aggages-search

IB Express has to be booked under an IB flight code, not I2.

Iberia does extend OW benefits to passengers ticketed in basic fares. Sometimes you may run into situation where agent try to charge you; in this case, you may want to kindly ask them to ask supervisor to overwrite the luggage fee.
In Madrid, you are also entitled to Fast Track and lounge invitation with one guest.