Hats off for trying SELPA, however since the "share deal" the company has no real assets and no spare cash and it's a bit difficult to see what can be gained from this challenge other than being a inconvenient pain in the arse.
I'm sure it's been ventilated before, but if the union felt the transfer was illegal why didn't they take action at the time? and if the company had been doing well, would they have bothered at all.
More effective action may be gained from refusing to handle any NAS aircraft in Spain, surely the airport staff will side with SELPA?
Notwithstanding the above, its still a crap deal for the crews, and some are still in denial of their fate...