CROSSOVER ON VISUAL APCH.

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WE WERE BEING VECTORED FOR THE VISUAL APCH 28R AT SFO. BAY APCH GAVE US A HDG OF 100 DEGS AFTER XING SFO VOR. THEY GAVE US A DSCNT FROM 5000 TO 4000' AND TOLD US TO EXPECT APCH CLRNC IN 12 MI. AT 10 DME WE WERE CLRED DOWN TO 3000'. AT 11 DME WE WERE ISSUED A HDG OF 240 DEGS. WHILE IN THE TURN APCH ISSUED TFC--AN MLG AT 1 O'CLOCK AND AN ACR SMT AT 12 O'CLOCK. WE HAD BOTH IN SIGHT AND CONTINUED DOWN TO 3000' AND 240 DEG HDG. WE MAINTAINED 30 DEG BANK AT 160 KTS. BAY TOLD US TO MAINTAIN VIS AND CLRED US FOR THE VIS APCH 28R ALONG SIDE THE SMT. THE SMT WAS TOLD TO MAINTAIN VIS WITH US AND CLRED FOR THE VIS 28L. THE SMT APPEARED TO BE AT 4000-4500' ON A 310-330 DEG HDG CONVERGING TOWARDS US. IT WAS NEVER CLEAR TO US FROM THEIR CONVERSATION AS TO WHETHER THEY HAD US IN SIGHT. THEY SAID TO BAY THEY 'JUST HAD A LIGHT TWIN LIKE AN SMT PASS UNDER (THEM) ABOUT 1500'.' OUR RATE OF TURN AND ACR LATE APCH CLRNC AND POOR LINE UP VECTOR CAUSED BOTH ACFT TO FLY SLIGHTLY THROUGH THEIR RESPECTIVE RWY # CENTERLINES. REALIZING THE SITUATION BAY APCH SWITCHED RWYS FOR BOTH OF US. NO EVASIVE ACTION WAS REQUIRED. WE WERE BOTH HANDED OFF TO TWR AND NOTHING FURTHER WAS SAID. THIS SITUATION COULD HAVE BEEN PREVENTED IF: 1) EXTENDED OUR DOWNWIND BEFORE TURNING US ONTO VIS APCH; 2) TURNED US ONO APCH EARLIER; AND 3) LESSER INTERCEPT ANGLE FOR WINGS.