COMMUTER HAS TCASII RA; RESPONDS.

Narrative

WE WERE ARRIVING FWA. WE DSNDED TO 7000 FT PROCEEDING DIRECT TO THE ARPT. A BE-58 WAS DEPARTING FWA; AND ASSIGNED 6000 FT. THE BARON ACQUIRED US VISUALLY; AND ACCEPTED A CLB THROUGH OUR ALT. THE RANGE AT THIS POINT WAS 2 1/2 MI ACCORDING TO TCASII; AND HE WAS IN OUR 12 O'CLOCK POS. AT APPROX 500 FT BELOW US TCASII ISSUED A CLB RA. PRIOR TO THIS; THE CTLR HAD ISSUED A DSCNT CLRNC TO US BASED ON THE OTHER ACFT HAVING ACQUIRED US VISUALLY. I WAS NOT HAPPY WITH THAT CLRNC; AND DID NOT ACCEPT IT. WE DID FOLLOW THE RA; AND I SAW THE BARON PASS OFF OUR L SIDE ABOUT 100 FT BELOW AND ABOUT 600 FT HORIZLY. I TALKED TO THE APCH SUPVR WHO SAID THIS WAS 'LEGAL.' I HAVE A FEELING THAT LEGAL AND SAFE ARE 2 DIFFERENT WORLDS. I AM NOT COMFORTABLE DSNDING THROUGH CONVERGING TFC'S ALT BASED ON THE OTHER ACFT MAINTAINING VISUAL SEPARATION ON US; AND I DON'T HAVE HIM IN SIGHT. A CONTRIBUTING FACTOR TO US NOT ACQUIRING THE OTHER ACFT WAS THE FACT THAT WE WERE ON THE END OF A 2 DAY TRIP WITH SCHEDULED REDUCED REST (8 HRS OF REST). BOTH THE FO AND MYSELF FELT TIRED AND NOT AS SHARP AS WE COULD HAVE BEEN. THIS PRACTICE HAS TO STOP BEFORE SOMEONE IS FOUND TO BE ASLEEP AT THE WHEEL. IF WE HADN'T BEEN ON TOP OF THIS SIT; IT COULD HAVE HAD BEEN A VERY LOUD CRUNCH.