B737 AT 3500 FT BEING VECTORED TO MIA EXPERIENCED TCASII RA WITH ACFT ON FINAL TO PARALLEL RWYS.

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FLT FROM CLT TO MIA; TOLD TO EXPECT RWY 9. VECTORED DOWNWIND N OF ARPT THEN VECTOR ON BASE LEG ACROSS FINAL FOR RWY 8. GIVEN DSCNT FROM 4000 FT TO 1500 FT. WE WERE IN AND OUT OF CLOUDS. CTLR WARNED/ADVISED MD80 TFC ON FINAL THAT HE WAS XING US IN FRONT OF HIM. HE THEN ADVISED US OF THE MD80. WE WERE IN CLOUD AT THE TIME. HE (THE CTLR) THEN ASKED THE MD80 IF HE HAD US IN SIGHT; THE MD80 REPLIED NO; BUT HE HAD US ON TCASII. THE FO WAS FLYING AND I WAS MONITORING. THE CTLR GAVE OUR TFC RANGE AS 4-5 MI BUT I WAS BECOMING CONCERNED WITH A TCASII TARGET CLOSER TO 2 1/2 MI. JUST AS I WAS ABOUT TO SAY SOMETHING TO THE CTLR; HE TURNED US TO 120 DEGS; WITH THAT WE GOT A TA; FOLLOWED IMMEDIATELY BY AN RA; 'MONITOR VERT SPD.' VSI WAS ILLUMINATED IN A RED BAND FROM APPROX A 2000 FPM CLB DOWN TO 6000 FPM DSCNT. NO GREEN LIGHTS. AS THE CLOSEST AREA NOT IN THE RED WAS A CLB I BEGAN TO INITIATE ONE; AT THAT TIME THE FO SAW THE MD80 COME OUT OF A CLOUD DIRECTLY AHEAD OF US DSNDING THROUGH OUR ALT; THE HORIZ SEPARATION WAS 1/2 MI OR LESS. WE CONTINUED OUR PULL UP AND TURNED RIGHT BEHIND THE MD80. WE RPTED THE RA TO ATC. THE CTLR SOUNDED A LITTLE BEWILDERED; STATING HE THOUGHT WE EACH HAD A VISUAL. PERHAPS HE MISUNDERSTOOD THE MD80'S 'I GOT HIM ON TCASII;' FOR 'I GOT HIM.' MY FO; WHO SIGHTED MD80 JUST AS TURN TO 120 DEGS WAS GIVEN; IS SURE WE WOULD HAVE COLLIDED HAD WE NOT PULLED UP; TURNED BEHIND MD80 WHEN WE DID. I BELIEVE THE TURN TO 120 DEGS CONFUSED THE TCASII CAUSING IT TO TRY TO RECOMPUTE ITS RA. WHY ATC TURNED US TO 120 DEGS MAKES NO SENSE. IF WE HAD TAKEN THE TURN; COLLISION WOULD HAVE BEEN UNAVOIDABLE. I TRULY BELIEVE THE CTLR THOUGHT THE MD80 HAD A VISUAL ON US. WHEN THE MD80 PLT SAID 'I GOT HIM ON TCASII' I BELIEVE ALL THE CTLR HEARD WAS 'I GOT HIM.'