B737-400 ACFT TAXIING WAS CLRED TO FOLLOW ANOTHER B737; BUT THE CLRNC WAS TO FOLLOW A B737-200. RPTR CAPT ACFT WAS IN LINE BEHIND OTHER B737'S WHO WERE CLRED ACROSS THE RWY AND RPTR THOUGHT HE WAS SUPPOSED TO FOLLOW. TWR CTLR EXPECTED RPTR ACFT TO TURN ON TXWY TO FOLLOW A DIFFERENT ACFT. ACFT HOLDING FOR TKOF HAD TO ABORT THE ROLL DUE TO THE RWY TRANSGRESSION.

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TAXIING OUT AT PHL WE WERE THE #3 ACFT FOR TAXI AT SPOT X. PHL WAS DEPARTING RWY 9L. THERE WERE ACFT LINED UP ON TXWYS K; J (OPPOSITE DIRECTION) AND P (OTHER SIDE OF THE RWY). THERE WERE 2 COMPANY B737'S AHEAD OF US AT SPOT X AWAITING TAXI CLRNC. EACH RECEIVED CLRNC TO CROSS THE RWY AND JOIN THE LINE ON TXWY P. OUR CLRNC WAS 'TAXI TO RWY 9L; FOLLOW THE COMPANY 200 SERIES.' THERE WERE NO MAJOR DISTRS; BUT I FIXATED ON THE WORDS 'FOLLOW YOUR COMPANY B737' AND; IN FACT; THE FO READ BACK 'RWY 9L FOLLOW THE COMPANY.' I FOLLOWED THE B737-300 AHEAD ACROSS THE RWY; WHEN I SHOULD HAVE TURNED TO FOLLOW THE B737-200 IN LINE ON TXWY K. THERE WAS A B727 IN TKOF POS ON RWY 9L WHEN ALL 3 OF US CROSSED RWY 9L. ACCORDING TO ATC; THE B727 WAS CLRED FOR TKOF AS THE ACFT AHEAD OF US CROSSED. HIS TKOF CLRNC WAS CANCELED WHEN WE ENTERED THE RWY. HE HAD BEGUN HIS TKOF ROLL. WE HAD THE PVD ATC SUPVR ON THE JUMP SEAT. ALL 3 OF US CHKED THE POS OF THE B727 AS WE ENTERED THE RWY. HE WAS STILL STATIONARY AS THE NOSE OF OUR ACFT NEARED THE RWY CTRLINE. NONE OF US SAW HIM BEGIN TO MOVE. ALL 3 OF US BELIEVED THAT WE WERE TO FOLLOW THE B737-300 ACROSS THE RWY. NONE OF US RECALLED HEARING '200 SERIES.' THIS WAS A CLASSIC CASE OF A SOMEWHAT VAGUE CLRNC; BUT MORE IMPORTANTLY A CREW HEARING WHAT THEY EXPECTED TO; TUNING OUT THE REST. WE WERE 1 ACFT LENGTH BEHIND THE ACFT XING IN FRONT OF US; THEREFORE SOME PART OF ONE OR BOTH ACFT HAD TO BE ON THE RWY WHEN THE B727 WAS ISSUED TKOF CLRNC. OBVIOUSLY NEITHER TWR NOR B727 VERIFIED THAT THE RWY WAS CLR PRIOR TO ISSUING AND ACCEPTING TKOF CLRNC. PHL VERY MUCH NEEDS TWR CTLED STOP BARS AT ALL INTXNS DUE TO THE HIGH NUMBER OF RWY XINGS REQUIRED THERE.