AN EMB120 PIC'S RPT ON A POTENTIAL CONFLICT WITH AN SF340 ON A PARALLEL DEP PROC FROM LAX. IT COULD HAVE BEEN AN NMAC BUT FOR THE CAPT'S LEVELING OFF TO AVOID THE SAAB 340. THE 2 ACFT HAD A SIMULTANEOUS DEP FROM RWYS 25L&R WITH THE SAAB 340 MAKING A VECTORED L TURN IN FRONT OF THE EMB120.

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OUR FLT WAS ON POS AND HOLD ON RWY 25L AT LAX. A SAAB 340 ACFT WAS CLRED FOR TKOF ON RWY 25R. AS THE SAAB BEGAN ITS TKOF ROLL; OUR FLT WAS CLRED FOR TKOF. AS WE LIFTED OFF; LAX TWR TOLD OUR FLT TO KEEP THE SAAB ON OUR R SIDE AND MAINTAIN VISUAL SEPARATION. (WE NEVER SAID WE HAD THE SAAB IN SIGHT.) OUR FLT WAS GOING TO SAN DIEGO AND THE SAAB ACFT WAS DESTINED FOR PALM SPRINGS. BOTH ACFT WERE ON THE SAME SID AND BEGAN L TURNS TO 200 DEGS AT; BASICALLY; XING THE SHORELINE. THE SAAB WAS THEN SWITCHED TO DEP AND WAS GIVEN A FURTHER L TURN TO 110 DEGS. WITH THIS NEW HDG; THE SAAB TURNED DIRECTLY IN FRONT OF MY ACFT; AND THERE WAS NO WAY TO KEEP IT OFF MY R SIDE. THE SAAB WAS SLIGHTLY ABOVE MY ACFT AND CLBING; SO I ELECTED TO LEVEL AND THEN DSND 300 FT. I WENT UNDER THE SAAB BY 800 FT AND RECEIVED A TA. EVEN IF I HAD CALLED THE SAAB IN SIGHT AND STATED THAT I COULD MAINTAIN VISUAL SEPARATION; THERE IS NO WAY I COULD HAVE ANTICIPATED THAT DEP CTL WOULD TURN THE ACFT DIRECTLY IN FRONT OF ME. UPON LNDG IN SAN DIEGO; I CALLED SOCAL TRACON AND LAX TWR. THE LAX TWR CHIEF INDICATED THAT THE LAX CTLR MADE A MISTAKE AND SHOULD HAVE DEPARTED MY FLT FROM RWY 25R AND THE SAAB FROM RWY 25L. LAX TWR FURTHER INDICATED THAT SOCAL DEP'S RADAR CANNOT DETERMINE WHICH ACFT DEPARTED WHICH RWY. SOCAL DEP ASSUMED THAT THE SAAB DEPARTED RWY 25L AND MY FLT DEPARTED RWY 25R. WITH THIS SIT; THE SAAB'S L TURN TO 110 DEGS WOULD HAVE TAKEN THE ACFT FURTHER AWAY FROM MY ACFT; RATHER THAN STRAIGHT INTO OUR ACFT (IE; A CONFLICT WOULD NOT HAVE OCCURRED).