A few years back (3-4?) I faced a scene in a gate at CPH. A GA was scolding a pax next to me for flying on some kind of staff voucher/pass SK ticket like the ones you are discussing. It was an SK flight, extra Schengen, but I think short haul. He was dressed in DY-branded wear and had a pilot suitcase with him. The GA has guessed out that he is a Norwegian pilot and started to question how he got the ticket. He said he is married to an SK FA. Then he got a lecture that his wife could loose a job for that, because these tickets are not supposed to be used to get other airline's staff to get to work. he was apologetically explaining (not believably though) that he is flying to visit family. He was allowed to board after some debate. Just a data point.