ACR X RWY INCURSION HAD LTSS FROM ACR Y TKOF. SYS ERROR.

Narrative

BEFORE BEGINNING TAXI; BOS GND ADVISED OF WIND CONDITIONS AND REQUESTED ACR X INTENTIONS FOR TKOF. (ATIS WAS RPTING RWY 31L FOR LNDG AND RWY 27 FOR TKOF; WITH WINDS OF 300 DEGS AT 20 KTS GUSTING TO 26.) BECAUSE I WAS ADMINISTERING AN IOE FLT WITH A LOW TIME FO; I REQUESTED RWY 31L FOR TKOF. WE WERE GIVEN TAXI INSTRUCTIONS TO RWY 31L; 'VIA TXWY A TO C; HOLD SHORT OF RWY 27.' WHEN WE ARRIVED AT THE HOLD SHORT POINT; GND CLRED US TO 'CROSS RWY 31.' WE THEN READ BACK 'ROGER; CLRED TO CROSS RWY 27 (EMPHASIS ON RWY 27); AND CONTINUE TAXI.' GND CTLR ACKNOWLEDGED CORRECTION. ABOUT THE TIME OUR ACFT BEGAN TO MOVE I NOTICED THAT THE A-300 Y THAT HAD BEEN HOLDING IN POS ON RWY 27 APPEARED TO BE MOVING. I IMMEDIATELY PULLED OFF PWR AND APPLIED STRONG BRAKING. WE STOPPED SHORT OF HOLD SHORT LINE FOR RWY 27; SO WE NEVER ACTUALLY STRAYED ONTO RWY 27. Y ROTATED IN FRONT OF US. I DESCRIBED WHAT HAD OCCURRED TO THE GND CTLR; AND WITHOUT MISSING A BEAT HE SIMPLY SAID 'ROGER.' THIS REACTION WOULD NOT SEEM TO BE THE APPROPRIATE RESPONSE GIVEN THE POTENTIAL DEVASTATING ACCIDENT THAT COULD HAVE TAKEN PLACE.