Planning for this extension has been on BART's mind for but studied seriously since at least 2003. The study initially looks at just going down the I-580 Median. Boooorrrrinnnggg and cheap. From the BART study done by Nelson Nygaard below...
The study also looks at connections to Walnut Creek, but we're going to focus on the Pleasanton area extension. Also, BART is building an infill station at Dublin. It's represented below as a black and white dot. The blue line is the Dublin/Pleasanton BART line which goes to SFO. The green line is the ACE commuter rail that goes to the Central Valley. This was also the route for the Altamont high speed rail alignment I believe.
But here are possible alignments. The yellow line is my favorite. It goes through the dense neighborhood being created to the north (orange box) and moves along vacant land that could be zoned for dense office and residential. It also passes the Livermore Airport, downtown livermore and gets right next to the Livermore National Labs facility which the north side of the station area could provide park and ride facilities for those driving over the Altamont who didn't use the ACE Train.
The red line uses the freeway until it gets to a crossover point. The cross over point allows the transit to move onto the ACE ROW and stop at stations up there. It along with the freeway median all the way out to Livermore plan are the cheap ways out. They might be cost effective but they do not provide opportunity for livable neighborhoods around the stations, since there is are 4 lanes of the freeway running on each side of the train. This will make the stations fairly auto/park n ride oriented. Also, if
Any thoughts? (The right side is cut off. Click on the picture to get a full view)