Not ex-Mil, ex Victorian Railways. The VR
GY wagons were the universally common 4 wheeled wagon for most of the 2nd half of the 20th Century. As they were withdrawn from servce, some were cut up for scrap, others sold by auction to find all kinds of 2 lives. Underframes of many types of rail wagons are often used as small bridges by private property owners.
As for location, looks like Rutherglen to Wangaratta for all I know.