Swiss is really odd when it comes to lounge access.

I've been in the F lounge in ZRH when flying on TK in Economy, just upon showing my (LX branded) HON card. But when flying on 4U, even HONs only get access when their ticket is on LX stock, but not on 4U stock. They have a printed out list of pax who have booked the 4U flights on LX ticket stock.