A B737-500 FLT CREW THOUGHT THEY WERE CLRED INTO POS AND HOLD WHEN THEY WERE NOT AT LAS; NV.

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START AND TAXI OUT WERE NORMAL. WE WERE CLRED TO TAXI TO RWY 25L AT LAS. AS WE APCHED THE DEP END; THERE WERE 2 ACFT AHEAD OF US. ONE WAS IN POS AND ROLLED AS WE WERE ABOUT 2000 FT FROM THE END. A COMPANY ACFT WENT INTO POS AT THAT TIME. I THEN PUSHED THE FLT ATTENDANT CALL BUTTON AND AFTER A SOMEWHAT LONGER THAN USUAL TIME; GOT A RESPONSE FROM THE FLT ATTENDANTS AND CALLED FOR THE BEFORE TKOF CHKLIST. AS WE WERE COMPLETING THE CHKLIST; COMPANY ROLLED ON TKOF AND I WENT AROUND THE CORNER AND INTO POS. AFTER WE WERE ON THE RWY; MY FO ASKED IF WE WERE CLRED ON THE RWY (HE LATER TOLD ME THIS WAS BECAUSE HIS LIGHTS WERE NOT ON). AFTER TKOF; WE GOT A MESSAGE FROM CTR TO CALL LAS. WHEN WE LANDED; I MADE THE CALL AND THE TWR CTLR SAID HE HAD CHKED THE TAPES AND WE WERE NEVER CLRED ONTO THE RWY. OBVIOUSLY BOTH MY FO AND I FEEL THAT WE WERE CLRED INTO POS AND HOLD. THE ONLY RATIONALE I CAN THINK OF FOR OUR ACTIONS IS THAT WE ARE STILL NOT COMPLETELY COMFORTABLE WITH THE NEW PROCS. IN THE PAST; WE WOULD DO THE 'BELOW THE LINE' ITEMS ONLY WHEN CLRED ONTO THE RWY. DOING THESE ITEMS CONFERRED A TACIT CONFIRMATION THAT THE CLRNC HAD BEEN GIVEN. I BELIEVE THAT IN THIS CASE; DOING ESSENTIALLY THE SAME CHKLIST CONVINCED US THAT WE HAD IN FACT BEEN CLRED.