60cm gauge was quite widely used in France and elsewhere for narrow gauge operations (besides metric gauge). As you mentioned it has been used by the military during WWI (French as well as British troops used 60cm gauge), but also in a lot of civilian industrial and agricultural railroads (quary, mines, ...). A large part of the 60cm gauge equipment was manufactured by a company named 'Decauville', which has a comprehensive catalogue of motive power (steam engines), rolling stock (passenger and all sorts of freight cars) and tracks (including portable track!).
Benoit