ACR FLC OF MLG DSNDING INTO EWR RECEIVES TCASII ALERT AND RA.

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ENO.RBV1 TO EWR AND BEING ON RADAR VECTORS FOR APCH TO RWY 22L. DISTANCE WAS APPROX 15-20 NM NW OF TEB HDG APPROX 090 DEGS AT 5000 FT. INITIALLY RECEIVED TFC ALERT FROM TCASII; DID NOT SIGHT ACFT VISUALLY. THE ACFT WAS BELOW US. AT ABOUT THE 2 O'CLOCK POS AND CLBING. DUE TO SUN GLARE ON TCASII; COULD NOT READ THE OTHER ACFT ALT. AFTER 5-10 SECONDS; WE THEN RECEIVED A TCASII RA TELLING US TO DSND. WE THEN INITIATED A DSCNT THAT WAS IMMEDIATELY FOLLOWED BY A TCASII RA TELLING US TO CLB. WE THEN INITIATED THE CLB; AT WHICH TIME THE APCH CTLR TOLD US TO STOP MANEUVERING. THE CTLR WAS VERY BUSY DURING THIS TIME AND DID NOT MENTION THE ACFT UNTIL AFTER OUR TCASII RA AND DEVS. AFTER THE CTLR'S INSTRUCTION TO STOP OUR CLB; THE FO FINALLY GOT THE OTHER PLANE VISUALLY JUST BELOW ABOUT 2 O'CLOCK POS ON APPROX 290 DEG HDG. WE THEN RECEIVED CLR OF CONFLICT MESSAGE ABOUT 5 SECONDS LATER. THIS WHOLE SCENARIO TOOK APPROX 20 SECONDS. LATER; 2 PAX INQUIRED ABOUT THE NEAR MISS (THEY SAW THE PLANE) AND THE DEV MANEUVER. CONSIDERATIONS: THE APCH CTLR WAS EXTREMELY BUSY WITH ACFT AND WE WERE BEING VECTORED WAY TO THE NW OF OUR USUAL ARR RTE. IT IS UNCLR IF THE CTLR KNEW OF THIS ACFT OR ITS POS BEFORE OUR DEV. HE EITHER BECAME AWARE AFTER THE FACT OR WAS TOO BUSY TO INFORM US OF THE PLANE'S POS.