I was informed by this directly at the UX counter in Madrid early November... however the staff would not reveal (or did not know) the details of suma.
Based in Spain, you would think there would be plenty of opportunity to earn FB miles with UX however the earning restrictions are so strict and it seems like only the most expensive fare classes actually earn miles... I have only ever earned on UX domestic in the business class.
Probably the only unpublished benefit of being FB gold when flying UX is that they regularly upgrade due to overbooking.
Iberia anyhow has a much more competitive product, better frequencies, a much nicer terminal in Madrid and lounge access on domestic, so Suma will have its work cut out to capture Iberia's clientele.