I don't think Silvers get fast track at all airports and as you say it varies.

I believe it's only an actual published benefit for LHR, LGW and JFK.

See this thread but here's what it says re GVA. Perhaps a regular can give an accurate update.

https://www.flyertalk.com/forum/brit...arding-24.html

I've no idea if that works but this is from the Fast Track Thread (See the Wiki)

GVA - Geneva Boarding: Boarding: Yes. Security: Yes (requires scanning of BP - no non-status guests in Y. If status in Y, or CE on BACF, you'll need a BP printed at the check-in counter; app and home-printed BPs do not currently work).

Pete