it’s rather hard to find BSS counters that shows the call setup time. You can see the average duration of the SDCCH seizure, but this takes into acount the SMS duration, Location Upd duration, IMSI attach duration and call setup duration altogether.
The best way is to perform Abis Traces or Drive Tests, so you know exactly what is the duration of call setups for the few calls you’ve traced.
Pix