ACR X TCASII RA HAD NMAC LTSS FROM TWIN BEECH. EVASIVE ACTION TAKEN. SYS ERROR.

Narrative

ACR X WAS CLRED FOR A VISUAL TO RWY 25L TO FOLLOW OUR COMPANY STRAIGHT-IN FROM THE E. WE HAD JUST PASSED THE 10 DME RESTR FOR 6000 FT TO REMAIN IN THE CLASS B AND BEGAN DSNDING; WHILE CONFIGURING FOR THE APCH. THE TCASII HAD NUMEROUS TARGETS AND INITIALLY HAD SHOWN THE COMPANY AIRPLANE WE WERE FOLLOWING AS A CONFLICT. AS WE SLOWED UP AND THE COMPANY GAINED ADEQUATE SPACING ON US; THE TCASII VERBALLY ANNOUNCED TFC FROM OUR L. I LOOKED BUT COULDN'T FIND HIM. THE TCASII ANNOUNCED; 'REDUCE DSCNT' WITH A RED TARGET AT 11 O'CLOCK. I ACQUIRED VISUALLY THE TFC; TOLD THE COPLT HE WAS LOW AT 11 O'CLOCK COMING RIGHT FOR US. WE LEVELED OFF AT 5700 FT JUST AS APCH FREQ BECAME BLOCKED WITH SEVERAL XMISSIONS AND AN EXCITED VOICE YELLING; 'ACR X LEVEL AT 5700 FT NOW!' I SAID; 'WE'RE LEVEL AT 5700 FT; AND WE HAVE THE TWIN BEECH IN SIGHT PASSING UNDERNEATH US.' WE MISSED THE ACFT BY 200 FT THANKS TO THE TCASII WARNINGS. THE TWR CTLR ASKED US TO CALL HIM ON THE PHONE WHEN WE LANDED. THE SUPVR SAID IT WAS AN INTERNAL PROB AS THE CTLR WAS WORKING BOTH ACFT; HAD FAILED TO ADVISE EITHER AIRPLANE; AND LOST SEPARATION ON THE BEECHCRAFT AND US. I STATED I WAS NOT FILING A NEAR MISS; BECAUSE WE HAD ACQUIRED THE ACFT VISUALLY; WE DID NOT INITIATE EVASIVE ACTION; AND I COULD SEE WE WERE GOING TO MISS HIM. I WAS IN A POS TO MANEUVER OUR AIRPLANE AWAY FROM THE BEECHCRAFT HAD HE BECOME A COLLISION THREAT. I ASKED IF THE TWIN WAS FILING A RPT; AND THE CTLR SAID NO.