San Diego light rail (with wires) has freight service at night on several lines and might be mentioned as a prototype for SMART+NWP. The Oceanside/Escondido light rail line, though using diesel cars instead of electric, is similar. However, their service is qualitatively different than what NWP would provide - it's at most 1 slow train a night over short (maybe 20 miles or so end to end) lines serving a small number of on-line customers and a little through freight to Tijuana. Heavier freight movements to the port area use separate lines. SMART+NWP would have to handle whatever freight is coming off a potentially 300-mile railroad (more likely 100 mile for the foreseeable future). I just don't see shared light rail passenger service (electric or diesel) working on that kind of freight line - to have any flexibility for schedules (passenger and freight) you would almost have to use FRA-compliant equipment which increases the cost substantially.