2 ACR ACFT AT PHL LNDG SIMULTANEOUSLY ON RWY 27R AND RWY 35 HAVE AN NMAC NEAR THE RWY THRESHOLDS.

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WE WERE CLRED VISUAL APCH RWY 27R; THEN CLRED TO LAND. BOTH APCH AND TWR ADVISED US OF TFC LNDG RWY 26 AHEAD OF US. WE ADVISED BOTH THAT WE HAD IT IN SIGHT. (IT WAS NO FACTOR AND APPEARS UNRELATED TO THIS INCIDENT.) UNBEKNOWNST TO US; A JETSTREAM 32 WAS CLRED TO LAND ON XING RWY 35. WE NEVER HEARD THEM CHK IN. PERHAPS WE WERE RUNNING CHKLISTS. AT APPROX 400 FT AGL; NEARING THRESHOLD; I NOTICED A TARGET ON THE TCASII INDICATING 200 FT ABOVE US. I BEGAN SCANNING FOR AN ACFT THAT I HAD JUST HEARD TWR CLR FOR TKOF FROM RWY 27L. I SAW THAT ACFT ON THE RWY STILL AND DIRECTED MY SCAN OFF TO MY L. AT APPROX 200 FT AGL; I SAW THE JETSTREAM OVER THE RWY 35 THRESHOLD; ON WHAT I'M SURE WAS A COLLISION COURSE WITH US. I IMMEDIATELY TOOK THE CTLS FROM THE FO; COMMANDED MAX PWR; BEGAN A 45 DEG BANKING CLB IN AN ATTEMPT TO STAY E OF RWY 35. ALMOST IMMEDIATELY AFTER OUR EVASIVE MANEUVER BEGAN; THE LCL CTLR ISSUED WHAT I BELIEVE TO BE A CASUAL GAR TO THE JETSTREAM CREW. I FOUND OUT LATER THAT THIS CREW SAW OUR ACFT AS WE BEGAN TO GO AROUND. THEY TURNED STEEPLY TO THE L TO AVOID US BEFORE OR AT THE SAME MOMENT THAT ATC ISSUED THEIR GO AROUND. HAD THEY MAINTAINED RWY HDG FOR ONLY A MOMENT OR TWO; A COLLISION MAY HAVE OCCURRED BECAUSE I'M NOT SURE WE WERE ABLE TO STAY E OF THEIR RWY. WE CONTINUED THE CLBING TURN TO RETURN TO THE FIELD FOR AN UNEVENTFUL LNDG. I BELIEVE THAT THE RESPONSIBILITY FOR SEPARATION LAY WITH THE LCL CTLR. AT THE LEAST; WE SHOULD HAVE BEEN MADE AWARE THAT TFC WAS TO LAND ON THE XING RWY. HOWEVER; I (OR MY FO WHO WAS THE PF) MIGHT HAVE HEARD THIS OTHER CREW ACCEPTING OR THE CTLR GIVING A LNDG CLRNC. ALTHOUGH I CREDIT THE TCASII WITH GIVING ME THE FIRST INDICATION (THERE WAS NO AURAL WARNING SINCE WE WERE BELOW 1000 FT. I ONLY HAPPENED TO NOTICE THE TARGET) OF TFC; IT APPEARED TO BE 30 DEGS TO THE L OF THE NOSE; NOT 45 DEGS; WHICH IT ACTUALLY WAS. ALSO; BECAUSE THE '+02' SYMBOL WAS NOT ACCOMPANIES BY A 'CLBING' SYMBOL; I SHOULD HAVE KNOWN THAT THE TARGET WAS NOT THE TFC DEPARTING RWY 27L. I MIGHT HAVE INVOLVED MY FO IMMEDIATELY UPON NOTICING THE TCASII TARGET. AN EXTRA SET OF EYES MAY HAVE HELPED; ALTHOUGH HE WAS FLYING.