From Wiki, which quotes an article from Harpers:
The division superintendent of a great Western railroad recently explained to me his reluctant part in the creation of the socially disintegrating conditions out of which the migratory workers and the rebellious propaganda of the I. W. W. have sprung. "The men down East," he said, "the men who have invested their money in our road, measure our administrative efficiency by money return—by net earnings and dividends. Many of our shareholders have never seen the country our road was built to serve; they get their impression of it and of its people, not from living contact with men, but from the impersonal ticker. They judge us by quotations and the balance-sheet. The upshot is that we have to keep expenses cut close as a jailbird's hair. Take such a detail as the maintenance of ways, for example—the upkeep of tracks and road-beds. This work should be going on during the greater part of the year. But to keep costs down, we have crowded it into four months. It is impossible to get the number and quality of men we need by the offer of a four months' job. So we publish advertisements broadcast that read something like this:
Men Wanted! High Wages!
Permanent Employment!
"We know when we put our money into these advertisements that they are— well, part of a pernicious system of sabotage. We know that we are not going to give permanent employment. But we lure men with false promises, and they come. At the end of four months we lay them off, strangers in a strange country, many of them thousands of miles from their old homes. We wash our hands of them. They come with golden dreams, expecting in many cases to build homes, rear families, become substantial American citizens. After a few weeks, their savings gone, the single men grow restless and start moving; a few weeks more and the married men bid their families good-by. They take to the road hunting for jobs, planning to send for their families when they find steady work. Some of them swing onto the freight-trains and beat their way to the nearest town, are broke when they get there, find the labor market oversupplied, and, as likely as not, are thrown into jail as vagrants. Some of them hit the trail for the woods, the ranches, and the mines. Many of them never find a stable anchorage again; they become hobos, vagabonds, wayfarers—migratory and intermittent workers, outcasts from society and the industrial machine, ripe for the denationalized fellowship of the I. W. W."
In 1917, Railroads in America employed 1.8m people. This was more than any other industry. (Railroad employment peaked soon afterwards, in 1920).
Source: https://www.aar.org/keyissues/Documents/Background-Papers/A-short-history-of-US-Freight.pdf
With so many people employed, all sorts of dubious employment practices were probably found somewhere, but perhaps not as pervasively as the author cited might imply.
Working on the rail right of way (either to build it, or to maintain it) was a large employer of unskilled labor. When building the Central Pacific railroad, Irish workers and Chinese workers were employed in large numbers. (80% of the Central Pacific construction workforce - or 12,000 workers were Chinese in 1868)
Source: http://www.pbs.org/wgbh/americanexperience/features/general-article/tcrr-cprr/
Management liked Chinese workers because they found them to be good workers and reliable and less expensive (Chinese workers were paid $30/month on the Central Pacific Construction, while Irish workers were paid $35/month).
The temporary nature of railroad maintenance work (once the railway was built) was probably more due to weather making it only practical to perform track maintenance projects in the summer on Northern or Mountainous railroads, rather than due to some nefarious plot by the distant money men in the East. The same pattern is true today for road maintenance in most northern parts of North America.
If you were running a railroad, you could not perform maintenance projects efficiently in the winter. You would not want to do more than urgent maintenance in the spring (because your railroad should be making money transporting new immigrants and farm equipment before planting). You would not want to do maintenance during the autumn (busiest time on the Western Roads, hauling the harvest to market). This left the summer, as the best time to maintain the Road.
Unskilled workers have always been vulnerable to less than scrupulous employment practices, but it seems to have possibly been a stretch to blame seasonal railroad employment for a proliferation of hobos, wayfarers, and Wobblies.