The last time I saw the dual gauge track in the BART Hayward shops it was a dead end spur into a shop building, probably intended for unloading new BART cars from flatcars. IT was a three rail spur with one rail being common to both gauges. Similar arrangements were used in Alamosa on the D&RGW. Just outside of the shop, the BART and WP tracks diverged and the BART track merged into the yard while the standard gauge WP spur joined the WP main. There was one frog in the junction, and only one switch point. I think that the WP spur may have been abandoned later, but I am sure that the three rail spur still exists in the shop building.