Nice to hear from you again in these days !
Your search by car travelling in theory could give you a better feeling of where there is the type of terrain we are looking for,especially those mysterious “smooth”, even, not rocky, background green hills maybe dominated by olive trees (as the close up view in the movie shows -the one you posted originally with the train + horse approaching the station). But the olive trees in that close up do not appear to be at such regular patterns as one can see in for example the subbetica area where hills are less dark green due to great space between trees.
The building I mentioned is only a possible small verification IF we find the actual location which of course would be easy to recognise anyhow from other details, so it will offer very little as a clue.
But my hopefully correct calculation in some previous post about the geographical positioning of the double railway tracks (due to the shadows direction) must in my view rule out tracks that go from southsoutheast to northnorthwest or with an even greater angle towards west. This should be another evidence which rules out Piñar and other possible stations in similar orientation. Statistically the tracks in Almeria,Murcia,Valencia usually tend to go to the west (more than the east) and therefore, all things equal, should be of less probability than for example tracks in Malaga, Cordoba, Sevilla, Jaen which I think should more often point more to east. Of course there are exceptions.
Regarding via verdes there are several also in south east in Murcia for example where you sometimes can travel via Google Street view. No new promising clues there though so far. Via verdes seem to be everywhere nearly in abundance,but so far I have no promising tracks. As you mentioned ESPERANZA might be along a regular double track and via verdes usually are single tracks.
So we should possibly be looking after double railway tracks (around 1966) that point more to the east than to the west if you consider the direction of the train in the movie as going forward more to the east.
I tried to look for such railway tracks with the help of https://www.vialibre-ffe.com/pdf/ViaDoble_España_21092010.pdf?fbclid=IwAR2U6iNMoQT75qg8kmrOYmPxZj6ydHbw1BHPVzyB3C7x98esoBGQwABvu2E see for example the map on PDF page 9 and maybe some other link regarding the state of conditions around 1966.
The important clue of the configuration of the telegraph poles should lead us to ESPERANZA, IF there in theory for example exist records of such details. As mentioned before the same configuration has appeared in photos from the Murcia province, but no promising tracks there so far.