Look. I have a BMI Gold card and have been admitted to the Star Alliance lounge at ZRH (Concourse B) departing on an LX flight (and arriving at ZRH on a train). This seems to be an informal, interim policy (in formal terms you should not be entitled to access), but I didn't have to beg for access. I have been in economy on these flights, usually travelling to London (LCY).

Thw Swiss lounges in Concourse E and the main Airside Center between Concourses A and B will NOT let you in unless you have status with LH or LX, at least until April when LX will join *A.