Which Idaho Railroad?

I am hoping some of our railroad and interurban historians out there can help identify this photograph. Written on the far right side of the railroad car are clearly the letters "IDAHO." I cannot tell if there is more lettering further to the right as that end of the car is beyond the frame of the picture. Perhaps there is a connection to the Boise & Interurban Railway, Boise Railroad Co., or Boise Valley Railroad Co. but no "Idaho" in those names? Or maybe the Washington, Idaho & Montana Railroad Co.? The railroad worker sitting second from the left is wearing a cap with I believe the letters "CB&(R or B). Sorry if the letters are not real clear in this scan. Email me or click on "Post a Comment" below if you have information or know any of these guys. Click on the pic to enlarge and then again for an even larger view. 

 "The most intensively surveilled sector of the late-nineteenth-century America was the railroads, then flinging their silver tracks across the continent. As the burgeoning transportation of goods and passengers across state lines outran the shelter of traditional law enforcement, the trains and their contents—as well as bridges, tracks, and terminals—were increasingly at the mercy of hijackers, hooligans, resentful farmers, and angry homesteaders. But an even greater threat came from railroad employees, who, with astonishing regularity, appropriated fares and freight for their own accounts." "The surveillance of railroad employees inevitably involved detective agencies in the very activity that for centuries had repelled Anglo-Saxons on both sides of the Atlantic: spying. Not surprisingly, both the agencies and their clients preferred the term testing. Those who engaged in it were called 'testers' or 'spotters.' But, to many American workers and much of the public, they were nothing more nor less than spies." "For years, the Thiel agency marshaled the largest force of railroad spotters. Gus Thiel had been one of Pinkerton's most valued operatives as an agent during the Civil War, then in the Chicago office. Disgruntled over some now-forgotten slight, in 1873 he formed his own firm, based first in St. Louis and later in Chicago—a personal betrayal Allan Pinkerton never forgave." "So identified was Thiel with spying on railroad employees that in 1889 a disgruntled railroad man, writing as Martin P. Wheeler, penned a diatribe called 'Judas Exposed; or the Spotter Nuisance,' lampooning Thiel's agency as 'Zeal's Railroad Inspection Service.' Zeal did most of his recruiting in 'the saloons and low resorts of St. Louis,' where he had no difficulty finding agents with the 'faculty for sneaking, lying and dissembling even to [their] most intimate friends and relatives." — Big Trouble by J. Anthony Lukas