Just saw this interesting bit of news today:
Short and medium distance train journeys in Spain will be free of charge for four months from September, Prime Minister Pedro Sánchez announced on Tuesday (12 July).
All commuter trains (Cercanías and Rodalies) and mid-distance regional lines covering journeys of less than 300km (Media Distancia routes) run by the national rail operator Renfe will be free from 1 September to 31 December.
The 100 per cent discount is only available on multi-trip tickets, not singles. Travel on other services, including long distance trains and those operated by other companies, will not come under the measures.
This could mean free train travel between cities like Barcelona and Seville or Madrid and Bilbao - if you are willing to commit to buying a season ticket.