FLC OF AN MD88 RESPONDED TO A SIMILAR SOUNDING CALL SIGN AND STARTED TAXIING IN POS TO HOLD WHEN THEY NOTICED ANOTHER COMPANY ACFT ON THE OTHER SIDE OF THE RWY. THEY HAD JUST PASSED THE HOLD LINE WHEN THEY RECOGNIZED THEIR ERROR.

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DUE TO WINDS; CVG WAS USING RWY 27 FOR ALL ARRS AND DEPS. RWY 27 HAS 2 ENTRY TXWYS FOR FULL LENGTH DEPS; K2 AND M2. MOST ACFT; INCLUDING OURSELVES; WERE GOING TO ENTER RWY 27 VIA TXWY K2. WHEN WE WERE #1 FOR DEP OFF RWY 27; TWR CLRED WHAT WE THOUGHT TO BE OUR ACFT INTO 'POS AND HOLD.' WE READ BACK THIS CLRNC. HOWEVER; THIS CLRNC WAS APPARENTLY FOR A COMPANY ACFT WITH AN ALMOST IDENTICAL CALL SIGN. THIS ACFT WAS LOCATED ON M2 (OPPOSITE US) AND WHOSE 3 DIGIT CALL SIGN WAS THE SAME AS OURS EXCEPT FOR THE MIDDLE DIGIT. THIS AMBIGUITY WAS RESOLVED WHILE WE WERE STILL WELL CLR OF THE RWY PROPER; BUT THE NOSE OF THE ACFT WAS SLIGHTLY PAST THE HOLD LINE. ATC WAS ADVISED AND AFTER THE OTHER ACFT DEPARTED; WE DEPARTED UNEVENTFULLY. CONTRIBUTING FACTORS WERE: 1) BOTH ACFT WITH SIMILAR CALL SIGNS WERE BOTH #1 FOR TKOF ON THE ONLY RWY IN USE. 2) NEITHER ACFT KNEW THE OTHER ACFT CALL SIGN. 3) ANTENNA FARM IN CLOSE PROX TO APCH END OF RWY 27 ENGENDERS FREQ BLEED-OVER AND CAN MAKE COMS DIFFICULT. 4) WE DID READ BACK OUR INSTRUCTIONS BUT PROBABLY THE TWR EXPERIENCED SIMULTANEOUS READBACK/HEARBACK PROBS FROM 2 ACFT. THERE IS NO WAY TO CONFIRM A READBACK OF THIS NATURE GIVEN CURRENT RADIO PROCS.