NMAC BTWN AN SMA TWIN LEVEL OFF LAX SHORELINE AND AN ATX TURBOPROP COMMUTER CLBING UP THROUGH THE TWIN'S ALT.

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AT APPROX XX20 PDT; I WAS RETURNING TO SANTA MONICA; CA; ARPT FROM SAN DIEGO; FLYING A LIGHT TWIN. FLT FOLLOWING HAD BEEN UTILIZED THROUGHOUT. APCHING LAX; FROM THE S; I REQUESTED; AND WAS CLRED FOR THE 'SHORELINE APCH' AT 2500 FT. THIS REQUIRES A CLRNC SINCE IT IS IN CTLED AIRSPACE (CLASS B). XING JUST W OF THE S RWY COMPLEX AT 2500 FT AND ABOUT 1/2 MI OFFSHORE; I SAW A PAIR OF LNDG LIGHTS APCHING RAPIDLY FROM MY 1-2 O'CLOCK POS; AND CLBING TOWARD ME RAPIDLY. I TOOK EVASIVE ACTION BECAUSE THE 'SHORELINE APCH' RESTRICTS DEPARTING ACFT TO 2000 FT. JUST AS THE TWIN-TURBOPROP PASSED DIRECTLY UNDERNEATH; ITS CREW RADIOED TO DEP CTL THAT THEY HAD LEVELED AT 2200 FT JUST IN TIME TO AVOID AN ACFT. SOCAL ASKED IF THEY HAD RECEIVED A 2000 FT RESTR; TO WHICH THEY REPLIED IN THE NEGATIVE. AFTER LNDG; I CALLED THE SOCAL SUPVR WHO PROMISED TO FOLLOW-UP. WE SPOKE SEVERAL DAYS LATER AFTER THE TAPES WERE RECEIVED AND THE CAPT OF THE COMMUTER FLT WAS CONTACTED. THE TAPES REVEALED THAT THE INITIAL CLRNC FROM CLRNC DELIVERY WAS TO 3000 FT. HOWEVER; AT THE TIME OF THE TKOF RELEASE; A 2000 FT RESTR WAS GIVEN. THE TKOF CLRNC WAS ACKNOWLEDGED BY THE CREW; BUT NOT THE ALT RESTR; WHICH THEY DENY HEARING. ACCORDING TO SOCAL APCH; THIS IS THE SECOND SUCH INCIDENT IN THE PAST MONTH! I BELIEVE THAT ACKNOWLEDGING A RESTR ON RELEASE; SHOULD BE MANDATORY FOR THIS TYPE OF OP; AS WELL AS INCREASED VIGILANCE ON THE PART OF PLTS UTILIZING THE SHORELINE APCH.