It depends on the TRX’s configuration, e.g. if u the following distribution:
TRX1: BCCH+SDCCH+6TCH
TRX2: SDCCH +7TCH
TRX3:8TCH
TRX4:8TCH
then (6+7+8+8=29 for full rate & 29*2=58 for half rate) subscriber can talk at the same time & (8+8=16) subscriber can make call setup at the same time. So, it highly depends on the TRX channel configuration.
Regards,
Ibrahim