I am really not in a position to comment about the current situation in Spanish ATC. I have read a variety of inputs from both sides of the argument, both here and elsewhere and it seems to me that there are a good number of inconsistencies between the positions being espoused.
Looking specifically at the safety issue - as opposed to the multitude of contributory factors that might affect safety - it seems puzzling that no-one has mentioned any involvement the national regulator or National Supervisory Authority have and what, if any, actions they are taking. On the face of it, assuming that there really is a safety issue at stake, it would appear that the regulator/NSA is not actually doing its job. Is this correct?
It is, perhaps, interesting to note that there is an ICAO Universal Safety Oversight Audit of Spain scheduled for early July. Whilst this is most unlikely to result in any immediate changes to the situation, maybe it presents an opportunity to get an independent view on how Spain is providing its civil aviation services and how effectively it is conducting oversight of safety matters.