POTENTIAL CONFLICT IN APCH PROC.

Narrative

WHILE COMPLETING THE FLT FROM SYR TO LGA; WE WERE CLRED TO THE MASPETH TANKS FROM OVER THE EAST RIVER DUE N OF LGA. WE FLEW ON A CLRNC OVER KLGA TO THE EAST RIVER AND THEN GIVEN A CLRNC TO CROSS MASPETH TANKS AT OR ABOVE 2500 FT AND CLRED 'EXPRESSWAY VISUAL' TO RWY 31. UPON CHANGING TO TWR FREQ; TWR ASKED IF WE HAD AN ACR LGT IN SIGHT. MY CAPT'S RESPONSE WAS 'NO; BUT I'LL PROBABLY SEE HIM IN A SECOND OR SO.' I CONTINUED THE APCH; THE EXPRESSWAY VISUAL APCH TO RWY 31. UPON TURNING AROUND SHEA; TRANSITIONING TO THE FINAL; LGA TWR GAVE US A CLB TO 3000 FT; WE COMPLIED. THE OTHER ACR WAS STRAIGHT IN TO RWY 31; APPROX 1 - 1 1/2 MI OFF THE END OF RWY 31. WE RECEIVED A CLRNC BACK TO MASPETH TANKS; AT OR ABOVE 2500 FT; THEN WE WERE CLRED FOR THE 'EXPRESSWAY VISUAL' AND LANDED UNEVENTFULLY. WHEN ASKED BY MY CAPT 'WHAT'S GOING ON' AND ALSO A COMMENT BY THE CAPT ASKING THE CTLR 'WHAT'S ACR Y DOING;' INFERRING HE WAS NOT ON THE EXPRESSWAY VISUAL. THE CTLR SAID HE OR WE WERE WONDERING THE SAME THING. SUPPLEMENTAL INFO FROM ACN 242752: ATC WAS VERY RESPONSIVE WHEN THEY SAW THAT WE WERE INSIDE THE OTHER ACFT. I FEEL THE OTHER ACFT WAS PRIMARILY RESPONSIBLE FOR THE INCIDENT. HAD HE FLOWN THE PRESCRIBED GND TRACK WE WOULD NOT HAVE BEEN INSIDE OF HIM. LATER I FOUND OUT HE MAY HAVE BEEN ASKED TO EXTEND HIS BASE.