BECAUSE OF A WT PROB; THE FLC ON A B727 AT EWR REQUESTED RWY 4R. THEY TAXIED OUT BTWN THE PARALLEL RWYS AND WERE INSTRUCTED TO HOLD SHORT OF RWY 4R. A SHORT TIME LATER THE TWR CLRED THE B727 INTO POS AND HOLD ON RWY 4L. THE FO ACKNOWLEDGED RWY 4L BUT THEY TAXIED ONTO RWY 4R RESULTING IN 2 ACFT GOING AROUND.

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WE WERE CLRED TO TAXI TO RWY 4R AT EWR. THE NORMAL DEP RWY IS 4L; BUT DUE TO OUR WT WE REQUIRED THE LONGER RWY (RWY 4R). GND CLRED US ACROSS RWY 4L AND TOLD US TO HOLD SHORT OF RWY 4R (OUR REQUESTED RWY). WE WERE HOLDING SHORT AT THE END OF RWY 4R WHEN THE TWR CLRED US INTO POS AND HOLD. AS WE STARTED ONTO THE RWY I SAW A COMMUTER PLANE BREAK OUT OF THE CLOUDS FOR MY RWY. I STOPPED SHORT OF THE RWY; BUT PAST THE HOLD SHORT LINE. TWR TOLD THE ACFT AND A SUBSEQUENT ACFT TO GAR AND WE CONTINUED INTO POS. AS IT TURNS OUT; TWR HAD CLRED US INTO POS FOR RWY 4L. SINCE WE WERE HOLDING SHORT OF RWY 4R AND HAD NO ACCESS TO RWY 4L; WE ASSUMED THAT WE WERE CLRED INTO POS ON THE RWY WE WERE HOLDING SHORT OF. TO MAKE MATTERS WORSE; MY FO READ BACK THE INCORRECT CLRNC (RWY 4L). THE TWR HAD LOST TRACK OF US AND CLRED US INTO POS FOR A RWY THAT WE HAD NO ACCESS TO. I AM ASSUMING THAT THEY LOST CTL OF WHO WAS WHO. WE HEARD WHAT WE WERE EXPECTING TO HEAR (IE; RWY 4R) AND IN DOING SO; DID NOT CATCH THE CTLR'S MISTAKE. THE LESSON TO BE LEARNED IS NOT TO EXPECT A CERTAIN CLRNC; AND TO LISTEN CAREFULLY FOR MISTAKES.