I would suggest that the Tucson group get in touch with San Francisco (if they have not done so already) when it comes to running vintage cars on the same track with modern units. The article refers to San Diego; as far as I know, the vintage cars in that city (refurbished ex-San Francisco, ex-St. Louis PCC's) have not gone into service. Note that SF Muni has had a collision between and LRV and a Milano tram, and is still running.