DHC8 CREW ON TAXI OUT FAILED TO HOLD SHORT OF THE ILS RWY 4 HOLD LINE.

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I WAS TAXIING THE ACFT FOR DEP AT LGA FOR TKOF AND HAD BEEN CLRED BY GND TO TAXI TO RWY 4. THERE IS A RWY HOLD SHORT LINE (DESIGNATED 'B4 HOLD LINE') PRIOR TO REACHING THE APCH END OF RWY 4. I THOUGHT THAT WAS OUR CLRNC LIMIT. AS IT TURNS OUT; THERE WAS A NOTICE ON THE END OF THE ATIS THAT ADVISED THAT LGA HAD AN ILS RWY 4 HOLD SHORT LINE PROGRAM IN EFFECT. AS WE PROCEEDED PAST THE ILS RWY 4 HOLD SHORT LINE; THE TWR OR GND (I AM NOT SURE WHICH) CALLED TO ADVISE THAT WE WERE SUPPOSED TO HOLD SHORT OF THE ILS RWY 4 HOLD SHORT LINE. THEY EXPLAINED THAT IT WAS FOR WINGTIP CLRNC WITH THE LNDG TFC. GIVEN THAT THE TFC ON FINAL WAS NOT YET CLOSE ENOUGH TO BE A FACTOR WE WERE INSTRUCTED TO CONTINUE TAXIING TO THE OTHER SIDE OF THE RWY AND CLR OFF ONTO TXWY AA; CONTINUE N AND TURN AROUND IN THE VICINITY OF TXWY AA AND TXWY CY. WHILE WE WERE ON TXWY AA; THE TFC THAT WAS ON FINAL TO RWY 4 LANDED WITHOUT INCIDENT. WE WERE THEN DIRECTED TO TAXI ONTO THE RWY A TXWY Y AND BACK-TAXI ON THE RWY FOR DEP. THIS WE DID AND WERE CLRED FOR TKOF. CONTRIBUTING FACTORS TO THIS OCCURRENCE INCLUDE THE FACT THAT I DID NOT LISTEN TO THE ATIS. (MY PARTNER HAD PICKED UP THE ATIS AND CLRNC). GIVEN THAT THE WX WAS CLR; EVEN IF I HAD HEARD THE ATIS; I AM NOT SURE I WOULD HAVE UNDERSTOOD THAT THE ILS RWY 4 HOLD SHORT PROGRAM WHILE IN AFFECT WAS APPLICABLE TO VFR WX AND FOR THE PURPOSES OF WINGTIP CLRNC WITH LNDG ACFT. ALSO; I BELIEVED THAT WE HAD BEEN CLRED TO TAXI TO RWY 4 WITHOUT ADDITIONAL INSTRUCTIONS TO STOP AT THE ILS HOLD SHORT LINE. I DID HEAR THE ACFT BEHIND US BEING INSTRUCTED TO STOP AT THE ILS HOLD SHORT LINE AFTER WE HAD PASSED IT.