B737 HAD A CLOSE ENCOUNTER WITH A SABRELINER ON TKOF ROLL.

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WE WERE TAXIING W ON TXWY K IN PHL BEHIND AN MD80. HE WAS INSTRUCTED TO CROSS RWY 9L AT TXWY T AND TO GET IN LINE BEHIND ACFT ON TXWY P AWAITING TKOF CLRNC. GND CTL ASKED US TO RPT HOLDING SHORT OF TXWY T ON TXWY K. WHICH I RPTED IMMEDIATELY SINCE WE WERE ALREADY THERE. GND THEN INSTRUCTED US TO CROSS RWY 9L ON TXWY T AND EXPEDITE TO GET IN LINE BEHIND ACFT ON TXWY P. AS WE TURNED ONTO TXWY T; I TURNED ON THE STROBES AND CLRED THE RWY TO MY R (W). WHEN I DID THIS; I NOTICED AN ACFT IN POS WITH LIGHTS ON. I THEN NOTICED MOTION ON THAT ACFT MOVING TOWARDS US. I INSTRUCTED THE CAPT TO STOP US AS I NOTICED THE ACFT MOVING. HE DID THIS IMMEDIATELY AND WE CAME TO A STOP ABOUT 30-40 FT PAST THE HOLD SHORT LINES. WE ADVISED GND OF THE PROB AFTER THE SABRELINER PASSED IN FRONT OF US AND THEY RECLRED US ACROSS THE RWY. GND TOLD US AFTER REVIEWING THE TAPES THAT THE SABRELINER HAD TAKEN OFF WITHOUT CLRNC. HE MISTOOK ANOTHER ACFT'S TKOF CLRNC ON RWY 8. SOLUTIONS TO THIS MAY INCLUDE 1 CTLR FOR EACH RWY; RATHER THAN US BEING ON GND AND TKOF CLRNCS BEING GIVEN BY TWR; EVEN THOUGH IT'S THE SAME CONCRETE; AND ALWAYS LOOK BOTH WAYS BEFORE XING THE ACTIVE.