OPERROR LTSS WHEN AN ACR MD80 TYPE ACFT AT 5000 FT CONFLICTS WITH AN ACR B757 AT 4200 FT IN AN UNRESTR CLB TO FL280. RPTR STATED THAT THE FO DSNDED TO 4000 FT WHEN THE OTHER TFC WAS OBSERVED AT 5000 FT. RPTR ALLEGES BILINGUAL FO VERIFIED THE CTLR WAS HAVING NON ESSENTIAL CHATTER WITH THE INBOUND ACFT WHEN RPTR WAS ATTEMPTING TO MAKE CONTACT WITH THE CTR AFTER FREQ CHANGE FROM THE TWR.

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ACR X WAS ISSUED THE FOLLOWING ATC CLRNC FROM CCS CLRNC DELIVERY THAT WAS USING GND CTL FREQ THAT DAY. 'ACR X IS CLRED TO MIAMI VIA UPPER AMBER 315; FL280. INTERCEPT THE MAIQUETIA 319 DEG RADIAL AND SQUAWK XXXX.' TCASII WAS TURNED TO TA/RA AS REQUIRED IN THE FINAL ITEMS OF THE TKOF CHKLIST AND NO TARGETS WERE NOTED AS WE POSITIONED OURSELVES FOR TKOF ON RWY 9. RADAR WAS ALSO TURNED ON FOR WX AVOIDANCE LATER ON IN THE FLT. THE ATIS GIVEN BY GND PRIOR TO TKOF HAD UNLIMITED VISIBILITY AND SOME CLOUDS AT FL250 (250 FT SCATTERED). RADAR ALSO SHOWED NO RETURNS. AS A MATTER OF HABIT; I HAVE ALWAYS HAD TCASII 'LOOKING UP' AND THE RADAR; IF ON; ALWAYS POINTING 12 DEGS UP FOR TKOF. WE WERE CLRED FOR TKOF WITH THE FOLLOWING CLRNC: 'ACR X; CLRED FOR TKOF CONTACT MAIQUETIA CTL AFTER TKOF.' ALL ASPECTS OF THE TKOF ROLL WERE UNEVENTFUL AS WAS THE INITIAL CLBOUT. AFTER TKOF WE EXECUTED A L TURN TO 290 DEGS TO INTERCEPT THE MIQ 319 DEG RADIAL. WE SWITCHED RADIOS TO MIQ CTL BY 2000 FT AGL AND TRIED TO RPT OUR ALT AND OUR CONTINUING CLB TO FL280. WE WERE UNABLE TO CONTACT MIQ CTL DUE TO NON ESSENTIAL CHATTER ON THE FREQ BTWN THE CTLR AND AN INBOUND ACFT. THIS WAS VERIFIED BY A BILINGUAL FO WHO WAS THE PF. THE CTLR QUERIED THE INBOUND ACFT AS TO WHAT WAS HIS ALT AND THAT HE DID NOT HAVE RADIO CONTACT WITH THE 'DEPARTING ACFT.' THE INBOUND ACFT RPTED TO BE AT 5000 FT. AT NO TIME DID WE HAVE A PRESENTATION OF THE INBOUND ACFT ON TCASII OR ON RADAR. ON A HDG OF 290 DEGS AND CLBING OUT OF 4200 FT; THE FO ALREADY AWARE THAT AN ALT CONFLICT WAS POSSIBLE WITH US CLBING AND AN UNKNOWN ACFT AT 5000 FT; STARTED TO LOOK FOR TFC AND ACQUIRED THE INBOUND ACFT; AN MD80 TYPE ACFT; APCHING US FROM OUR 4 O'CLOCK POS AND CLOSING IN ON A CONSTANT BEARING DECREASING RANGE. THE CONFLICTING ACFT WAS ON A HDG OF 270-300 DEGS. HE PUSHED THE NOSE OVER AND TURNED TO PARALLEL THE CONFLICTING TFC. WE LEVELED OFF AT 4000 FT; AND WATCHED THE MD80 TURN AND CROSS BEHIND US. NOW WE WERE BOTH QUERIED AS TO WHAT OUR ALTS WERE BY MAIQUETIA CTL. WE RESPONDED 4000 FT. THE ACR Y SAID 5000 FT AND NOW SUDDENLY THE MD80 SHOWED UP ON TCASII READING 4700 FT. THE QNH WAS 1014 MILLIBARS. THIS WAS THE FIRST TIME WE WERE ABLE TO TALK TO MIQ CTL AND WE RPTED THAT WE WERE LEVEL AT 4000 FT WITH A CLRNC TO CLB TO FL280. MIQ KEPT US AT 4000 FT FOR ABOUT ANOTHER 2 MINS AND CLRED US TO CLB TO FL280. THE REST OF THE FLT WAS UNEVENTFUL. I BELIEVE THAT THE OTHER ACFT WAS 300-700 FT VERTLY AND 1000-2000 YARDS. CAUSES AND EFFECTS: 1) MIQ GND CTL OR CLRNC DELIVERY ISSUED A CLRNC THAT IS NOT NORMALLY GIVEN. INTERCEPT THE 319 DEG RADIAL VERSUS BEING ASSIGNED A SID MARES 9. 2) MIQ CTL HAD UNNECESSARY CHATTER THAT WAS MORE OF A SOCIAL NATURE THAN OF AN ATC NATURE; THAT PREVENTED US FROM CHKING EARLIER TO IDENT A POSSIBLE MISHANDLED OR MIS-ISSUED CLRNC. 3) I FIRMLY BELIEVE THAT OUR TCASII WAS WORKING PROPERLY AT ALL TIMES AND THAT SOME IRREGULARITY OCCURRED IN THE OTHER ACFT'S XPONDER OR TCASII SYS. 4) IF IT WAS NOT FOR THE SPANISH SPEAKING FO WHO WAS ABLE TO GLEAN SOME SITUATIONAL AWARENESS FROM THE CTLR'S SPANISH CONVERSATIONS; I FEEL AS IF THE RESULTS WOULD HAVE BEEN MUCH CLOSER IF NOT TRAGIC.