ACR X TCASII RA WITH ACR Y CLB THROUGH ACR X ALT. EVASIVE ACTION TAKEN.

Narrative

ACR X FROM HPN-BWI WAS CLBING OUT OF 12000 FT AS DIRECTED BY NEW YORK APCH CTL ON 120.85; WHEN WE RECEIVED A TCASII TA FOR AN ACFT BEHIND; BELOW AND SLIGHTLY L OF US. THE TA QUICKLY ESCALATED TO 'CLB; CLB; CLB' AND 'INCREASE CLB' RA'S. WE INCREASED OUR RATE IN EXCESS OF 2500 FPM; BUT IT WAS CLR FROM THE TCASII PICTORIAL THAT THE INTRUDER WAS STILL OUT CLBING US. AS I BEGAN A TURN TO THE R; ACR Y BLASTED THROUGH OUR ALT APPROX 200 YARDS FROM OUR L WING TIP. ROCKED BY Y'S WAKE WE DEMANDED AN EXPLANATION FROM THE CTLR WHO SAID HE HAD CLRED Y TO CLB THROUGH OUR ALT AND HE ASKED Y TO CONFIRM THAT THEY HAD US VISUALLY. Y'S RESPONSE WAS AMBIGUOUS -- SAYING THEY HAD AN RA FIRST; THEN SAW US VISUALLY. EVEN IF Y HAD MISIDENTED US AND THEIR TCASII WAS INOP; NEW YORK APCH SHOULD NOT HAVE CLRED BOTH X AND Y TO CLB THROUGH THE SAME ALT ON VIRTUALLY THE SAME FLT PATHS. RADIO CONGESTION WAS A FACTOR THAT MADE IT NEARLY IMPOSSIBLE FOR X TO OBTAIN EARLIER CONFIRMATION ABOUT WHAT APCH CTL AND Y WERE DOING.