ATC ISSUED NEW CLRNC TO LTT ACR ACFT WHEN ATC WAS UNABLE TO CONTACT ANOTHER ACR MLG ACFT FOR AVOIDANCE INSTRUCTIONS OF POSSIBLE CONFLICT.

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FLT DEPARTED IFR BRIDGEPORT TO WASHINGTON NATIONAL. RTE BDR JFK CYN. N OF COYLE CHKED WITH NY FLT WATCH FOR CURRENT ENRTE WX. AT THAT TIME WE WERE IN UNLIMITED VFR CONDITIONS AND CANCELLED IFR. WE REMAINED IN THESE UNLIMITED VFR CONDITIONS FOR THE REMAINDER OF THE FLT. WE CANCELLED IFR AND REQUESTED FLT FOLLOWING. WE LEFT 12000 TO 14500 VFR. WE PROCEEDED SW OF COYLE DIRECT OTT. CONSCIENCE OF BWI-PHL ARRS AND DEPS; WE ASKED CTR IF A VFR DSCNT WOULD CAUSE A CONFLICT WITH ARR AND DEP RTES. CTR SAID NO CONFLICT. WE NOTIFIED CTR OF OUR VFR DSCNT FROM 14500 TO 8500 FT. APCHING 11800 FT MSL CTR MADE 2 CALLS TO AN ACR. THE CTLR NOTIFIED ACR OF OUR POS; ALT; VFR DSNDING TO 8500 FT; HIS CTL. ACR MISSED THE CALL. THE CTR REPEATED AN ABBREVIATED VERSION. ACR MADE AN INCOMPLETE AND INCORRECT READBACK. THE CTLR GAVE US SEPARATION WITH THE ACR BY INSTRUCTING US NOT TO DSND TO 8500 FT. THE CTLR ASKED US TO MAINTAIN 11500 FT. WE ACKNOWLEDGED; COMPLIED ON THE SAME FREQ AS ACR. WE THEN CALLED ACR IN SIGHT. WE FLEW LEVEL ABOUT 4 MORE MI; WHEN ACR STATED A TCASII EVENT HAD OCCURRED. ACR THEN DEMANDED A REASON WHY TFC CALLED AS LEVEL 8500 FT WAS ACTUALLY AT 11500 FT. CLRLY ACR WAS OUT OF THE LOOP. NOTE: OUR INQUIRY ABOUT CONFLICTS BEFORE DSNDING MAY HAVE INDICATED WE WERE CONCERNED; ALERT; AWARE AND INDEED ABLE TO ACCEPT THE CTLR'S REQUESTS; AFTER ACR FAILED. ALSO TCASII ALERTED THE ACR WHO WAS OUT OF THE LOOP. TCASII WORKS.