LCL CTLR ISSUED A TKOF CLRNC TO A CPR LR45 WHILE AN ACR B737 WAS DEPARTING ON AN INTERSECTING RWY.

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WE WERE CLRED INTO POS AND HOLD BY ORD TWR ONTO RWY 32R AT INTXN V. WE NOTICED AN AIRPLANE TO OUR L EITHER IN POS OR ON SHORT FINAL ON RWY 4L. AS WE TAXIED INTO POS; WE CONTINUED TO NOTICE THIS OTHER ACFT. IT APPEARED NOT TO BE MOVING SO WE ASSUMED IT WAS IN POS FOR TKOF. WE DID NOT HEAR A CLRNC FOR HIM TO TAKE OFF. THE ARPT TWR FREQ WAS FAIRLY CONGESTED. WE WERE THEN CLRED FOR TKOF AND BROUGHT PWR UP AT BIT. WE WERE STILL LOOKING L AT THE OTHER AIRPLANE AND TO OUR SURPRISE FINALLY REALIZED IT WAS MOVING. WE STOPPED AND 'CALLED FOR AN ABORT' (ON THE RADIO) BECAUSE ANOTHER AIRPLANE WAS GOING TO CROSS OUR RWY. THE CTLR KEYED UP; PAUSED; AND SAID THANK YOU. IT WAS DIFFICULT TO JUDGE AT NIGHT WHEN HE STARTED ROLLING; BUT PRETTY EVIDENT THAT IF WE HAD NOT ABORTED; IT WOULD HAVE BEEN A COLLISION AT THE INTERSECTING RWYS IF A CREW HAD BEEN THERE WHO WAS UNFAMILIAR AS TO WHERE TO LOOK AND PAY ATTN; IT MAY HAVE BEEN CATASTROPHIC. SUPPLEMENTAL INFO FROM ACN 689497: I AM AN ATC CTLR AT O'HARE ATCT. I WAS WORKING N LCL (126.9). I WAS DEPARTING RWY 14L; RWY 32R; AND RWY 4L AND WAS LNDG AND DEPARTING RWY 9L. I CLRED ACFT X INTO POS AND HOLD ON RWY 32R AT INTXN V; AND TOLD HIM OF TFC DEPARTING RWY 4L. I CLRED ACR Y; A B737 FOR TKOF ON RWY 4L. APPROX 30 SECONDS LATER USING ANTICIPATED SEPARATION BASED ON MY EXPERIENCE; I CLRED ACFT X FOR TKOF. SHORTLY THEREAFTER; ACFT X TOLD ME HE WAS NOT ROLLING BECAUSE OF XING TFC. IT WAS MY OBSERVATION THAT ACR Y WOULD BE THROUGH THE INTXN PRIOR TO ACFT X STARTING HIS TKOF ROLL.