MLG HAS TCASII RA; RESPONDS. ATC SAYS THEY KNOW NOTHING ABOUT THE ACFT.

Narrative

WE WERE LEVEL AT 11000 FT COMING INTO CVG ON THE MILAN 2 ARR. WE GOT A TA OF AN ACFT AT 12 O'CLOCK. IT APPEARED TO BE 500 FT BELOW US. AS ACFT GET CLOSER WE GOT AN RA FOR US TO DSND. CAPT DSNDED THE AIRPLANE AND WE LOST APPROX 500 FT AND THEN THE TCASII REVERSED ITSELF AND GAVE US A CLB. A CLB WAS INITIATED AND THEN THE CAPT SAW THE ACFT PASS OFF TO OUR L SLIGHTLY LOW. ATC THEN TOLD US THAT WE WERE TO MAINTAIN 11000 FT AND THAT WE HAD TFC AT 3 O'CLOCK. I ADVISED ATC THAT WE WERE RESPONDING TO A TCASII RA AND DIDN'T HAVE TIME TO TELL THEM. THEN I SAW THE ACFT THAT CTR WAS POINTING OUT ABOUT 2-3 MI OFF OUR R WING. I TOLD CTR ABOUT THE ACFT THAT HAD PASSED JUST TO OUR L AND WAS BEHIND AS NAV BUT HE SAID HE KNEW NOTHING ABOUT THAT ACFT. THE CAPT SAID HE RESPONDED TO THE RA BECAUSE HE DIDN'T KNOW IF THE OTHER ACFT WAS CLBING INTO HIM OR NOT. WE DON'T KNOW IF IT WAS A TCASII GLITCH OR IF THE VFR TFC (LOOKED LIKE A NAVY TRAINER; SMALL JET ORANGE AND WHITE) WAS VARYING HIS ALT. MY OPINION IS THAT IN THIS SIT HE; TFC; WAS PROBABLY CRUISING AT 10.5 AND NOT R ON HIS ALT. THE TCASII RA DSNDED US RIGHT INTO HIM. WE WOULD HAVE BEEN BETTER OFF WITHOUT IT.