ACR X HAD CONFLICT WITH SMA Y WHILE ON VISUAL APCH TO IDA ARPT. SEE AND AVOID CONCEPT. ARTCC RADAR CTLR FAILED TO ARTCC ATCT INTERFAC COORD ACR X WITH IDA TWR PRIOR TO CHANGING THE ACFT TO TWR FREQ. OPDEV.

Narrative

PROCEEDING TO IDA VOR AS FILED. WHEN WE RPTED IDA ARPT ZLC (134.5) TURNED US 20-30 DEG R; STATING 'VECTORS FOR VISUAL RWY 20 IDA.' APPROX ABEAM APCH END OF RWY 20 (5 MI AND 6000 AGL); ZLC CENTER ASKED IF WE STILL HAD THE ARPT. WHEN WE RESPONDED YES; HE CALLED TFC; CLRED US FOR THE VISUAL 20 AND SWITCHED US TO IDA TWR (118.5). WE DID NOT HAVE TFC VISUALLY BUT WERE SHOWING IT ON TCASII (IN TA/RA ACTIVE MODE). ACR X EXTENDED DOWNWIND; TURNING XWIND AT BEACON. I ELECTED TO HOLD L OF LOC COURSE FOR RWY 20 BECAUSE OF TCASII TARGET INDICATIONS. WE STILL DID NOT HAVE TFC VISUALLY. FO SWITCHED US TO TWR FREQ WITHIN A MOMENT OR 2 OF BEING CLRED BY ZLC CENTER. WE HEARD IDA TWR TELL THE TFC (SMA Y) THAT ACR X HAD JUST 'POPPED' UP AND TO BREAK OFF HIS APCH. AT APPROX SAME TIME; TCASII ISSUED A TA ON SMA Y. NEITHER OF US EVER SAW HIM; BUT TCASII INDICATED CLOSEST APCH WAS 1 MI/400 FT. NO RA WAS ISSUED BY TCASII. ACCORDING TO TWR; ZLC HAD NOT ADVISED HIM WE WERE IN HIS AREA AND HE DID NOT HAVE US VISUALLY. HE STATED NORMAL PROC WAS FOR ZLC TO BRING ACFT ON A 3000 FT AGL DOWNWIND; PASS IT ON TO IDA TWR. THEN SWITCH ACFT TO TWR. TWR THEN ISSUED CLRNC FOR THE VISUAL. I ELECTED TO CONTINUE THE APCH. WE WERE CLRED FOR BY ZLC THOUGH WE DIDN'T HAVE THE TFC VISUALLY. TCASII ASSURED US ADEQUATE SEPARATION. APPARENTLY; THERE WAS A COMS BREAKDOWN BTWN ZLC CENTER AND IDA TWR; RESULTING IN A BREAKDOWN OF NORMAL; BUT UNPUBLISHED PROCS.