Trailheads of the Sierra Vista Trail (on OpenStreetMap):
The trail on OpenStreetMap is labeled as such, and in most places is a dashed red line (wide enough for pedestrian/horse usage). The southern portions have it rendered as a dashed brown line (wide enough for motor vehicle usage).
I've GPS tracks in two segments: the first segment is from Anthony to Vado, which is unfortunately inaccurate because I became lost trying to hike it. The second segment is from Vado to Soledad Canyon.
You can load Sierra-Vista-Trail.kmz into Google Earth to visualize all the trailheads. Add the OpenStreetMap layer as a "Network Link" to compare it against to OpenStreetMap and the trail's actual route.