It has been threatened. I think the line to Leon is in serious danger
The line to Leon is different from the coast route, was built to take coal from Matallana to Bilbao (joins the Santander line at Aranguren) to use in the iron works, using iron ore from around Castro Urdiales. Latterly the coal was going to La Robla. I rode this line in early 1980s, was wonderful but very leisurely, took about 6 hours, 1 a day; the line closed soon after due to dodgy track, subsequently reopened. The luxury FEVE tourist train used to traverse it. Both ends have commuter traffic, the middle section is desolate & sparsely populated.