I have experienced IRROPS with SAS that caused them to rebook into LH, I was flying Plus but this meant the flexi economy fare with LH = no lounge access. However, due to status with Eurobonus, I was still given access. That is a risk though. Likewise, if you book a trip from e.g. BGO to LIS via SAS in Plus, they do not award business class or any rights for lounge acces, if the routing is through TAP at OSL.