As a general point, many airlines have their own versions of
- Basic / entry level fare, no checked bags (e.g. Aer Lingus Saver, Vueling Basic)
- Plus / next tier up, allowing at least one bag (EI Plus, VY Optima)
- PlusFlex / top tier economy, allowing more bags and more flexibility (EI Advantage, VY Excellence, though that overlaps business class).

Codeshares on BA appear to be pitched and built around the Plus fare level, in terms of overall fare pricing, seating options and baggage - not the entry level fare structure. Consequently if the basic fares are still going then BA codeshares can look quite pricey and poor value, but closer to travel, and taking moderate checked baggage into account the codeshares look far more interesting.

Broadly speaking travelling on Air Baltic, Aer Lingus, Vueling, Air Berlin, Iberia, FlyBe (etc) BA codeshares gets you at least one checked bag.