SEVERAL ACR ACFT FROM THE SAME COMPANY WERE OPERATING ON THIS ARPT AT THE SAME TIME. THE ATCT LCL CTLR GOT THE CALL SIGNS CONFUSED BTWN 2 OF THE ACFT AND GAVE A CLRNC 'INTO POS AND HOLD' USING THE WRONG CALL SIGN.

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AS WE WERE BEING PUSHED BACK FROM OUR GATE; WE HAD ANOTHER COMPANY ACFT WAITING FOR OUR GATE. AS WE STARTED ENGS; THAT ACFT PULLED INTO THE GATE WE HAD JUST VACATED. AT THE SAME TIME ANOTHER COMPANY ACFT CALLED FOR PUSH ON THE GATE NEXT TO THE ONE WE HAD JUST LEFT; BUT THERE WAS SOME CONFUSION ON THE CALL SIGN. THE CREW HAD MADE A MISTAKE AND USED THE INBOUND FLT NUMBER. THEY FINALLY GOT IT STRAIGHT AND USED ACR Y. GND THEN SUGGESTED THAT ACR Y HOLD THE PUSH FOR OUR ACFT X TO TAXI BEHIND THEM. ACR Y HELD THEIR PUSH. TAXI WAS ROUTINE WITH NO OTHER ACFT ON THE TXWY UNTIL OUR COMPANY ACR Y CALLED FOR TAXI. AT THIS POINT WE WERE APPROX 2000 FT FROM REACHING POINT 1 FOR TKOF. I HAD NOTICED SOME LIGHTS ON THE TXWY AND ASKED THE FO IF HE KNEW OF THEIR SIGNIFICANCE. AS WE RESPONDED; SEA TWR CLRED ACR Y INTO POS AND HOLD. BY THIS TIME WE WERE HOLDING #1 AND MISSED THE FACT THAT TWR HAD USED OUR OTHER COMPANY'S CALL SIGN. I BELIEVE THE FO RESPONDED WITH OUR CALL SIGN AND 'ON TO HOLD.' TWR THEN CLRED ACR Y FOR TKOF. AT THIS POINT BOTH THE FO AND I REALIZED THE TWR THOUGHT ACR Y WAS FIRST IN LINE AND WE HAD MISSED THE MISTAKE UPON TAKING TXWY. WE TOLD TWR WE WERE ACR X; AND ACR Y WAS STILL TAXIING. AFTER VERIFYING WE WERE ACR X; SHE CLRED US FOR TKOF. THE SIT I BELIEVE BEGAN WITH THE CONFUSION ON CALL SIGNS AT THE GATE. THEN; EVEN THOUGH I DON'T THINK OUR CONVERSATION ABOUT TAXI LIGHTS VIOLATED THE STERILE COCKPIT SINCE IT WAS OPERATIONALLY RELATED; IT DID BREAK OUR CONCENTRATION. JUST AS WE EXPECTED THE CLRNC FOR TKOF; WE HEARD WHAT WE EXPECTED TO HEAR AND MISSED WHAT WAS ACTUALLY SAID.