As a follow-up:

I picked up a 1930 copy of Milburn's The Hobo's Hornbook" today, and thought I ought to see what he gave for the line in question. He offers "It's the 'boes' accommodation." So. I decided to look a little further and got out Bill Yenne's The Romance and Folklore of North America's Railroads (Brompton Books, 1994). Hardly seems fair to add Yenne to the documentation list, as the text he prints seems to be taken from Milburn, verbatim, even to including "Now here's to Long Slim Perkins..." instead of Boston Blackey, Daddy Claxton, Clark, or whomever.
Long Steel Rail (thanks SINSULL!!!). He offers a text dating back to 1904 (copyrighted by William Kindt but with no author credited), which was based by Kindt on an earlier one dated 1882 titled "The Great Rock Island Route" (published in 1882, words and music by J. A. Roff). In Roff's text, the line is "There's a name of magic import and 'tis known the world through-out, 'tis a mighty corporation called the Great Rock Island Route." The 1904 publication changed it to the "Wabash Cannon Ball" and gave the line as "There's a name of magic splendor that is known quite well by all, 'Tis the western combination called the Wabash Cannon Ball." Okay. These pre-date Milburn, BUT... Cohen goes on to write:

... although early versions had many phrases and verses that clearly identified the song as a hobo song, these halmarks have tended to disappear from the lyrics. For example. the last line of the first verse used to contain the phrase "she's the 'boes' accommodation," but now it is generally rendered as "she's a regular combination" (Carter Family) or "modern combination" (Loy Bodine) or just "the combination (Acuff).

I think the hobos either originated the song and it was misunderstood by those commercializers who grabbed it from them as it went by, or the hobos took the 1904 song and made it their own with the quite understandable "'boes' accommodation."

Sandy