A CRJ200 APCHING DCA RECEIVED AN RA WITH TFC NOT IN SIGHT. ATC REPORTED THE TFC HAD THEM IN SIGHT.

Narrative

WE WERE ON THE FINKS7 ARR; SOMEWHERE AROUND JASEN. WE WERE BUSY DOING IOE AND DISCUSSING THE RIVER VISUAL RWY 19 THAT WAS COMING UP. THERE ALSO WAS SOME CONFUSION WITH THE CTLR WITH XING RESTRS. I BELIEVE THE CTLR THOUGHT WE WERE ON THE ELDEE ONE RNAV ARR. I THINK THE CTLR CALLED US AS TFC TO ANOTHER ACFT. THE OTHER ACFT CALLED US IN SIGHT. I THINK THE CTLR GAVE THE OTHER ACFT A CLB CLRNC AND A CLRNC TO MAINTAIN VISUAL SEPARATION WITH US. I DIDN'T LIKE THE SOUND OF THIS. I TURNED ON ALL MY LNDG LIGHTS. SHORTLY AFTER; OUR TCAS COMMANDED ABOUT A 2000 FPM CLB. WE COMPLIED WITH THE TCAS. THE OTHER ACFT PASSED OFF OUR R SIDE. THE CREW OF THE OTHER COMMENTED ON HOW CLOSE WE CAME. THE CTLR'S SPEECH WAS SOMEWHAT DIFFICULT TO UNDERSTAND. THE TCAS REVERSED AND GAVE US A DSCNT RA JUST BEFORE THE OTHER ACFT PASSED OFF OUR R. SUPPLEMENTAL INFO FROM ACN 727528: THE OTHER ACFT WAS AROUND OUR 1-2 O'CLOCK POS; 1500-2500 FT. APCH THEN ASKED US IF WE GOT AN RA ON THE OTHER ACFT AND I REPLIED WE DID. ON THE GND THE CAPT AND I DISCUSSED WHAT AND WHY THAT HAPPENED AND WE WERE BOTH CONFUSED HOW EXACTLY THIS TRANSPIRED. WE DISCUSSED THAT THERE WERE SEVERAL FACTORS INVOLVED: THE CTLRS SEEMED TO BE STRUGGLING A LITTLE AND WERE A LITTLE HARD TO UNDERSTAND. THERE WERE SEVERAL TFC TARGETS ON THE MFD; BUT I THINK THE OTHER ACFT ACTUALLY DID NOT HAVE A VISUAL ON US AND I DON'T THINK THEY HAD THEIR LIGHTS ON. I MAY HAVE ALSO BEEN A LITTLE OVERWHELMED AS BEFORE THIS HAPPENED THE CAPT HAD JUST BRIEFED ME ON THE VISUAL APCH FROM THE N AND HOW IMPORTANT IT WAS NOT TO GO E OF THE RIVER. AS MENTIONED BEFORE; IT IS STILL A LITTLE FUZZY AND IT IS VERY POSSIBLE I MAY HAVE MISSED A CALL FROM APCH.