I haven't heard of the Irish connection. This is from The Fiddler's Companion:

Result of search for "Orange Blossom Special"
ORANGE BLOSSOM SPECIAL. Bluegrass, Breakdown. USA. A Major. Standard. AAB + vamp. "One of the most popular fiddle tunes in modern history" (C. Wolfe, Devil's Box, Dec. 1982). Composed by Ervin T. Rouse (c. 1938), inspired by the railway train called the Orange Blossom Special's christening and inaugural run (from Miami to New York). Co-authorship is often credited to Florida fiddler Robert Russell "Chubby" Wise (1916-1996), although the copyright is in Rouse's name, supposedly due to Wise's assertion that 'there was no money in fiddle tunes and that Rouse could copyright it himself, for all the good it would do' (Wise drove a cab at the time). Wise himself maintained that he and Rouse were at the Jacksonville Seaboard Railroad Station when the train came through on its maiden run from Miami. Rouse suggested that they write a tune and Chubby agreed. The two went back to Wise's house and wrote the piece in forty-five minutes, while his wife cooked them breakfast. The tune was recorded by Ervin and his brother Gordon in New York in June, 1939, but the tune did not become a hit until Bill Monroe's recording of it in 1942 (with Art Wooten on fiddle). The first recording, however, appears to be that of Tommy Magness', who recorded "Orange Blossom Special" with Roy Hall's group in 1938. It was unissued at the time, says Jim Nelson, perhaps to avoid legal problems with Rouse and his record company, RCA Victor. He thinks Magness probably learned the tune directly from Rouse, but that he definately taught it to Wooten. Magness is credited with popularizing the melody and introducing the famous double-shuffle into the tune. There are persistent rumours that Wise or Magness lost their rights to "Orange Blossom Special" in a poker game. Source for notated version: Blaine Sprouse (Brody). Brody (Fiddler's Fakebook), 1983; pg. 210. Rounder 0117, "Blaine Sprouse." RCA Camden CAL-719, Bill Monroe- "The Father of Bluegrass Music." Mercury SRM 1-1058, Vasser Clements- "Superbow." Mercury SRW 16261, The Stanley Brothers- "Instrumentals Country Styfle." United Artists 9801, "Will The Circle Be Unbroken" (various artists). Stoneway 104, Chubby Wise- "Chubby Wise and His Fiddle." Gusto 104, Scotty Stoneman- "30 Fiddler's Greatest Hits." Starday SLP 268, Curly Fox (1963). Caney Mountain Records CLP 228, Lonnie Robertson (Mo.) - "Fiddle Favorites," c. 1971-72.

~Masato