AN SAAB 340 FLT CREW; TAXIING FOR TKOF AT BOS; TAXIED PAST THE HOLD SHORT POINT.

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UPON COMPLETION OF AFTER START CHKLIST; I CONTACTED BOS GND TO REQUEST TAXI CLRNC FROM RAMP TO DEP RWY. BOS GND TOLD US TO EXPECT A 30 MIN TAXI DELAY. WE REQUESTED CLRNC TO HOLD OFF THE RAMP IN ORDER TO CLR OUT FOR INCOMING TFC NEEDING TO PARK. BOS GND TOLD US TO TAXI TO RWY 9 AND HOLD SHORT OF THE BRAVO HOLD POINT. THE CAPT BEGAN THE TAXI AND CALLED FOR THE TAXI CHKLIST. I STARTED RUNNING THE TAXI CHKLIST AND WAS INTERRUPTED BY BOS GND INSTRUCTING US TO MONITOR TWR FREQ. I CHANGED TO TWR FREQ JUST IN TIME TO HEAR TWR INSTRUCT AN ACFT ON APCH TO RWY 4L TO GO AROUND. I LOOKED TO OUR 2 O'CLOCK POS AND SAW THE ACFT INITIATING A GAR. THE CAPT STOPPED THE ACFT. BOS TWR CONTACTED US AND ASKED IF WE WERE THE ACFT THAT HAD ENCROACHED ON THE ARR END OF RWY 4L BEYOND THE BRAVO HOLD POINT. IN FACT; OUR POS AT THE TIME WAS BEYOND THE BRAVO HOLD POINT. OUR ACFT WAS ON THE EXTENDED CTRLINE FOR RWY 9 ON TXWY B. I REPLIED IN THE AFFIRMATIVE TO BOS TWR. TWR INSTRUCTED US TO CONTINUE TAXI TO RWY 9. WE CONTINUED TAXI TO RWY 9 AND WERE CLRED FOR TKOF SHORTLY THEREAFTER. WE DID FAIL TO HOLD SHORT OF THE BRAVO HOLD LINE CREATING A SIT THAT CAUSED ANOTHER ACFT TO GO AROUND AT THE TWR'S INSTRUCTION. BOS TWR MAY HAVE FILED THIS OCCURRENCE AS A RWY INCURSION. I HAVE NO EXCUSE FOR THIS HAPPENING. MY LACK OF FAMILIARITY WITH BOS MAY BE A CONTRIBUTING FACTOR TO THIS OCCURRENCE. MY NORMAL STATUS IS LINE PLT DFW.