The train is no longer in service over the viaduct. A previous engine failure which left passengers stranded for many hours required extensive repairs which left the operating company in finanical difficulties.
It's hoped that another company can resume service, but in the meantime, a train known as Tren del Sol goes as far as Diego de Almagro. However, you can follow the route by car, with stops along the way to see the Inca ruins of Santa Rosa de Tastil, and to film condors before arriving at La Polvorilla for photo opportunities.
By road, you'll alos see the town of San Antonio de los Cobres, guanacos, vicuñas, llamas and other sights not seen from the train.