Does the los angeles subway uses the same signaling system as the san francisco bart?
Basically yes. However the frequency used in the audio frequency track circuits are lower then those used on bart. There a few other differences on bart that mostly have to do with automatically stopping trains at platforms.
The Los Angeles Red line uses the same basic signaling systems that are used on Atlanta's MARTA, Baltimore's Metro, Miami's Metro, PATCO Lindenwold Line and in Washington on WMATA metrorail. The signaling system is described in my post to your similar question in the metrorail signals thread in the Washington MetroRail forum.