ACR X RWY INCURSION. HAD LTSS FROM B727 ON TKOF. SYS ERROR.

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UPON ACR X'S TAXI OUT FROM OUR RAMP AT MEM; WE WERE TOLD TO FOLLOW A COMPANY DC10 ON TXWY V TO RWY 9 FOR DEP. GND CTL CHANGED THE DC10'S RWY TO RWY 18L; AND INSTRUCTED HIM TO CROSS RWY 9/27 AT TXWY B. WE WERE THEN CLRED TO HOLD SHORT OF RWY 9/27 AT TXWY B; AND EXPECT RWY 18L FOR DEP. WE HELD SHORT OF RWY 9/27 FOR LNDG TFC; AND AFTER TFC LANDED WERE TOLD TO CROSS RWY 9/27. (IN THE MEANTIME; A COMPANY B727 WAS CLRED INTO POS ON RWY 9.) WE WERE EXPLICITLY TOLD THAT THE B727 WOULD HOLD IN POS WHILE WE CROSS RWY 9/27. WE OBSERVED HIM IN POS ON RWY 9; AND WE BEGAN TO CROSS RWY 9/27. AS WE REACHED A POINT APPROX 1/3 TO 1/2 WAY ACROSS THE RWY; WE NOTICED THE B727'S LNDG LIGHTS ON AND THAT HE APPEARED TO BE ROLLING FOR TKOF. GND CTL THEN INSTRUCTED US TO CLR THE RWY IMMEDIATELY; AND WE MADE A HARD R TURN TO CLR RWY 9/27 AT 'V2' TXWY. WHILE WE WERE DOING THIS; THE B727 REJECTED; TURNED OFF RWY 9/27 AT TXWY C; EXITED THE RWY TO THE S; AND BEGAN TAXIING BACK TO RWY 9 FOR ANOTHER TKOF. AFTER WE WERE CLR OF RWY 9/27 ON TXWY 'V2;' WE WERE THEN INSTRUCTED TO TAXI VIA TXWY V TO TXWY S AND ACROSS RWY 9/27 VIA TXWY S. WE THEN MADE AN UNEVENTFUL TKOF ON RWY 18L. OBVIOUSLY COMS MUST HAVE BEEN BOTCHED/CROSSED BTWN THE TWR/GND CTLR. WE COMPLIED EXACTLY WITH THE CLRNC GIVEN US; AND BOTH MY FO AND I EXPLICITLY REMARKED TO EACH OTHER THAT THE 'COMPANY B727 WOULD HOLD IN POS FOR US' AFTER GND CTL TOLD US SO WHEN WE WERE GIVEN CLRNC TO CROSS RWY 9/27. OBVIOUSLY THE B727 MUST HAVE BEEN CLRED FOR TKOF BY THE TWR CTLR WITHOUT CONFIRMING WITH THE GND CTLR OF OUR CLRNC OR THAT WE WERE CLR OF THE RWY.