B737-300 CREW; ON TKOF ROLL ON RWY 9L AND A LNDG B737 ON RWY 22R ALMOST COLLIDED WHEN THE LNDG B737 ONLY HELD SHORT AT THE LAST SECOND.

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ORD WAS DEPARTING RWY 9L; WITH LNDGS ON RWY 22R TO HOLD SHORT OF RWY 9L. WE WERE CLRED FOR TKOF ON RWY 9L AND ADVISED ACR Y FLT XX WAS LNDG RWY 22R TO HOLD SHORT OF OUR RWY. WE COULD SEE ACR Y TOUCH DOWN AND DECELERATE AS WE BEGAN TKOF ROLL. HEARD ORD TWR INSTRUCT ACR Y TO TURN L ON TXWY C AND HOLD SHORT OF RWY 9L. ACR Y ACKNOWLEDGED; BUT DID NOT READ BACK HOLD SHORT PER LCL PROC ADVERTISED ON ATIS. AS WE ACCELERATED FOR TKOF ON RWY 9L; WE COULD SEE ACR Y CLR RWY 22R ON TXWY C AT A HIGH RATE OF SPD; CREATING QUESTION IN OUR MINDS AS TO IF THEY WERE GOING TO HOLD SHORT OF OUR RWY. I WAS JUST CONSIDERING ABORTING WHEN TWR SAID ENTHUSIASTICALLY TO ACR Y XXX TO STOP! I SAW THEIR ACFT ABRUPTLY STOP (LURCH) SHORT OF THE RWY 9L HOLD SHORT LINE; AND WE CONTINUED TKOF WITHOUT INCIDENT. TWR QUERIED ACR Y; 'YOU WERE GOING TO STOP; RIGHT?' TO WHICH THEY REPLIED 'YES; OF COURSE.' NO INCIDENT OR ACCIDENT OR VIOLATION OCCURRED; THANKS TO THE QUICK THINKING OF THE ORD TWR CTLR. IF THE ACR Y B737 HAD GONE AHEAD WITH THE RWY INCURSION; EVEN IF WE HAD INITIATED AN ABORT; IT IS DOUBTFUL THAT A COLLISION WOULD HAVE BEEN AVOIDABLE. SO; WHILE NOTHING ACTUALLY HAPPENED; IT WAS NOT TOO FAR FROM BEING CATASTROPHIC. I THOUGHT COMPANY AND ORD TWR SHOULD KNOW ABOUT THIS.