A JUMP SEAT RIDER HEARS THE ATCT CTLR AT IAH AND A B737 CREW IN POS CUT EACH OTHER OUT SEVERAL TIMES DURING A BUSY PERIOD.

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I WAS RIDING JUMP SEAT (ATC OBSERVER) IN AN MD80 (ACFT X) DEPARTING IAH RWY 26. WE WERE #8 FOR DEP AT XA00 WITH RAPIDLY APCHING TSTMS SHARPLY INCREASING THE URGENCY OF THE ACTIONS AND XMISSIONS OF PLTS AND CTLRS ALIKE. IAH TWR WAS SCRAMBLING TO GET ARRS DOWN ON ANY AVAILABLE RWY WHILE STILL MANAGING TO GET DEPS OUT. AT ONE POINT; B737 (ACFT Y) WAS TAXIED INTO POS AND HOLD FOR IN TRAIL SPACING. AFTER A SHORT DELAY TWR CLRED THE B737 (ACFT Y) FOR TKOF WITHOUT A RESPONSE. THIS WAS RPTED. THE TWR URGENTLY REQUESTED A RADIO CHK FROM THE PLT WHICH WAS ACKNOWLEDGED. THIS WAS FOLLOWED BY YET ANOTHER TKOF CLRNC. THE PLT THEN ASKED FOR A WIND CHK BUT HIS XMISSION WAS BLOCKED BY THE TWR. THE B737 (ACFT Y) CONTINUED TO HOLD AWAITING A WIND CHK. TWR FIGURED THAT THEY HAD LOST COM AGAIN SINCE THE B737 (ACFT Y) WAS NOT MOVING AND HAD NOT ACKNOWLEDGED THE TKOF CLRNC. BOTH THE B737 (ACFT Y) AND THE TWR MADE REPEATED ATTEMPTS TO RE-ESTABLISH COM BUT CONTINUED TO BLOCK EACH OTHER OUT. AFTER (WHAT SEEMED LIKE) SEVERAL MINS; OTHER ACFT ON FREQ JOINED IN THE FRAY TRYING TO SORT THINGS OUT; BUT ONLY ADDING TO THE CONFUSION. THIS POTENTIALLY DANGEROUS SIT COULD HAVE BEEN AVOIDED IF ANTI-BLOCKING DEVICES HAD BEEN INSTALLED ON THE ACFT RADIOS.