From browsing the web, I ran across an article by W E Crippen in the Western Union Technical Review for October, 1961, "The End of an Era":
Prior to 1914, "line gangs," as they were called, were housed either in hotels or in railroad owned boxcar outfits that were equipped with such bare necessities as double-deck bunks, pot-bellied stoves, wash bowls, oil lamps, and other appointments in keeping with the time.The outfits were gradually sold off between the 1940s and about 1960, with the material cars staying on for some additional years. I'm not sure exactly what service the material cars were in in the years after the outfits were sold. At least one of the material cars was sold to the Soo Line: Notice that this Soo Line car has a fishbelly center sill like the Ambroid car and the prototype 7559, but the other WUTX prototypes have straight center sills. After I found the Ambroid car at the top of this post, I found and restored a second car, which I now intend to repaint boxcar red and letter for the Soo Line car in these photos.By 1914, many of the original pole lines were in need of repair because of deterioration or because the ever increasing wire load had become too great for the old pole lines to carry. Thus was undertaken the beginning of a heavy reconstruction program that was to last until the latter part of the 1920's and the start of the depression. The program reached its peak between 1925 and 1930.
At the start of this program, The Western Union Telegraph Company foresaw the benefits that could be derived from having the line gangs housed in outfits that could be set out at any location at any time or that could be moved to emergency areas quickly, at a much lower cost than if they were housed in hotels, some of which might be long distances from the jobsites.
. . . a camp car shop was established at Chattanooga, Tennessee as a headquarters for all outfit remodeling, maintenance, and supplies. This shop flourished and was busy continually until about 1930, when it entered upon a decline in activity that continued until a few years ago when the servicing of outfits was no longer required. (The camp car shop was then converted into a shop for manufacturing and assembling equipment to meet other and present day requirements.)
At the peak of the heavy reconstruction period, between 1925 and 1930, there were about 120 of these outfits scattered throughout the United States. By that time, the type of railroad cars used and the arrangement of the associated equipment had been fairly well standardized. These later models consisted of two Pullman cars about seventy feet in length (one sleeping car and one dining car), two boxcars (one tool car and one material car), and a steel tank car (water car). In fact, No. 10 recently sold at Portland consisted of two Pullman coaches, two boxcars, one tank car, and associated equipment.