WITH A 'LINE UP AND WAIT' CLRNC AND LNDG TFC RPTED ON A 3 MI FINAL AT A FOREIGN ARPT; AN ACR'S CLRNC IS CHANGED TO 'HOLD SHORT ARRIVING TFC' AND AN ACFT PASSES OVERHEAD TO LAND LONG.

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WE WERE CLRED BY BARCELONA TWR TO 'LINE UP RWY 7; TFC (A COMMUTER JET) ON 3 MI FINAL.' THAT IS WHAT ALL 3 OF US IN THE COCKPIT HEARD; AND THAT IS WHAT THE FO READ BACK. NO FURTHER COMMENT BY TWR. WE SAW AN ACFT ON WHAT LOOKED LIKE A 3 MI FINAL; AND ALSO SAW AN ACFT ON OUR TCASII IN THAT POS. ASSUMING THAT IT WOULD BE A QUICK DEP; WE PROCEEDED TO TAXI TOWARDS RWY 7. OUR ANGLE ON THE APCH CORRIDOR PREVENTED US FROM NOW SEEING THE ARR TFC. WE HAD CROSSED THE ILS HOLD SHORT LINE; BUT NOT YET CROSSED THE ACTUAL RWY HOLD SHORT LINE; WHEN SUDDENLY TWR INSTRUCTED US TO 'HOLD SHORT OF RWY 7; ARRIVING TFC.' WE MADE A 180 DEG TURN AND TAXIED AWAY FROM THE RWY (NEVER HAVING ENTERED IT) AND REALIGNED; HOLDING SHORT. ABOUT THAT TIME WE SAW THE COMMUTER ACFT PASS WELL OVERHEAD; LNDG A WAYS DOWN THE RWY. NOTHING FURTHER WAS SAID; AND WE THEN PROCEEDED TO DEPART NORMALLY. AFTERWARDS; THE ONLY CONCLUSION WE COULD COME UP WITH WAS THAT TWR HAD SAID (OR THOUGHT SHE SAID) LINE UP 'AFTER' THE TFC; NOT BEFORE. A CONTRIBUTING FACTOR WAS THAT PARTICULAR TWR OPERATOR SPOKE WITH A FAIRLY HVY SPANISH ACCENT AND SPOKE VERY RAPIDLY; AND NEVER QUESTIONED OUR SUPPOSEDLY INCORRECT READBACK. NONE OF US QUESTIONED THAT WE DIDN'T HAVE ENOUGH TIME TO MAKE A SAFE TKOF WITH THE TFC WE SAW; BUT THERE WAS POSSIBLY A CLOSER ACFT THAT NONE OF US HAD SEEN. AT ANY RATE; NONE OF US WILL EVER LINE UP ON AN ICAO RWY AGAIN; WITH TFC ON 5 MI OR LESS FINAL; WITHOUT A DOUBLE CONFIRMATION -- ESPECIALLY WHEN LANGUAGE IS A FACTOR.