It looks like City Sightseeing (www.city-ss.es) have the Wally concession in Nerja so the tourist train could be here to stay, at least for a while.
City Sightseeing are involved in the hop-on/hop-off bus (and other) services in Spain, Europe and the rest of the world for that matter, often using open top red double-decker buses.
In Nerja, the new service departs from Plaza Cavana with the first train at 10:00. The journey lasts one hour in total with a second stop in calle La Cruz. The last train is 18:00.