LCL CTLR AT ORD CLRS A RJ FOR TKOF BEFORE A BAE-146 HAD CLRED THE RWY AFTER LNDG.

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I WAS FO OF ACR X; A 757; HOLDING ON TXWY P SHORT OF H WITH CLRNC TO FOLLOW AN INBND BAE-146 JET. THE BAE-146 JET LANDED ON RWY 9L; ROLLED OUT TO P AND TURNED RIGHT; BUT HELD SHORT OF H AND NEVER CLRED THE RWY. NOTICING A HEAD TO HEAD CONFUSION; MY CAPT FLASHED HIS TAXI LIGHT MULTIPLE TIMES TO VISUALLY REAFFIRM TO THE BAE-146 JET THAT WE WERE GIVING WAY. DUE TO THE FRENZIED PACE OF OPS AT CHICAGO; THE TWR CTLR HAD ALREADY CLRED A REGIONAL JET TO TKOF ON RWY 9L BEFORE THE GND CTLR HAD RECOGNIZED THE CONFUSION AND TOLD ACR Y (THE BAE-146 JET) TO CONTINUE ON 'H'. BY THE TIME ACR Y STARTED MOVING ACROSS THE RWY HOLD SHORT LINE ONTO H; THE REGIONAL JET WAS AIRBORNE AND APPROX 50 FT ABOVE THE BAE-146 JET. IT DOESN'T TAKE MUCH IMAGINATION TO VISUALIZE EVEN A 737 IN PLACE OF THE BAE-146 JET; WITH A LONGER TAIL STICKING OUT ON THE RWY AND THE TKOF ACFT DELAYING ROTATION DUE TO HEAVY WT ABORT; THEN WE WOULD BE LOOKING AT WHAT EVERYONE IS TRYING TO PREVENT WITH THE CURRENT SHOW OF ATTENTION TO RWY INCURSIONS. RWY INCURSIONS HAPPEN DUE TO INEXPERIENCE AND CONFUSION ON MULTIPLE PARTICIPANTS PARES. HERE'S AN EASY ONE TO SOLVE; BY ENSURING THE TWR CTLRS ABIDE BY FAR'S AND NOT CLR ANYONE FOR TKOF UNTIL THE RWY IS CLR. O'HARE NEEDS TO SLOW DOWN. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: RPTR STATED THAT THE BAE-146 COMING OFF THE RWY MAY NOT HAVE SWITCHED OVER RIGHT AWAY TO GND CTL AND STOPPED BECAUSE THEY WERE NOT SURE WHETHER TO WAIT FOR TFC TO PASS. RPTR SAID THE GND CTLR WAS ISSUING INSTRUCTIONS NON-STOP TO APPROX EIGHT ACFT AND FINALLY TOLD THE BAE-146 TO TAXI AND THAT TFC APCHING THE INTXN WAS HOLDING. HE SAID THE REGIONAL JET PASSED DIRECTLY OVERHEAD AT ABOUT 50 FT WHEN THE BAE-146 STARTED TO TAXI COMPLETELY CLR OF RWY 9L.