A B737 FLT CREW IS CLRED ACROSS RWY 4L AT BOS. THE CAPT NOTICES AN ACFT ON FINAL AND STOPS THE ACFT. THE OTHER ACFT GOES AROUND.

Narrative

APCHING 'TXWY B HOLD POINT' AT ABOUT 1 KT GND SPD; GND CTLR INSTRUCTED US TO TAXI; 'WITHOUT DELAY' ACROSS APCH END OF RWY 4L; TO HOLD SHORT OF RWY 4R AND TO CONTACT TWR ON (I DON'T RECALL FREQ). I ADDED MAX TAXI THRUST AND WE (RELATIVELY) SLOWLY MOVED FORWARD. AS FO WAS DIALING THE NEW FREQ I HEARD; 'ACR X STOP.' (FO CHANGED FREQ AT THAT TIME) WHILE AT THE SAME TIME OBSERVING AN ACFT ON APCH FOR RWY 4L AND REALIZING WE WOULD NOT BE ABLE TO CLR THE APCH END BEFORE ITS ARR (TOO HVY; TOO SLOW). I IMMEDIATELY (AND ABRUPTLY) STOPPED THE ACFT SHORT OF THE APCH PATH AS THE FO CHANGED RADIO FREQS. THE ACFT ON APCH PERFORMED A GAR AND ONCE WE REESTABLISHED COMS WE WERE INSTRUCTED TO CONTINUE OUR TAXI. NEITHER ATC NOR I ENGAGED IN ANY OTHER COMS ABOUT THE INCIDENT (VERY BUSY RADIO TFC). I DO NOT KNOW WHO INITIATED THE APCH ACFT'S GAR. I DO NOT KNOW IF THE 'STOP' WAS INTENDED FOR US (SAME COMPANY). I BELIEVE IT WAS INTENDED FOR US AND I BELIEVE THE GND CTLR MADE THE SAME CALCULATION I DID AT ABOUT THE SAME TIME; WE WOULD NOT CLR THE APCH PATH BEFORE THE APCHING ACFT'S ARR. I STOPPED THE ACFT ENSURING THE APCH PATH WAS CLR; BUT MAY HAVE THEREFORE FAILED TO COMPLY WITH AN ATC CLRNC.