From what I've read in several places, most of the Thomas engines that travel around (there are several, as I understand) are unpowered and the sponsoring railroad provides the power which is usually put at the end of the train so as not to detract from the real "star." I do believe there are one or two actual steam Thomas engines, however, although I don't know how they're prioritized in the requests for Thomas appearances. Regardless of which kind of Thomas appears, though, it evidently draws crowds galore and the kids love it, as Ms. Voss has indicated, and it provides enormous publicity for the sponsoring railroad. I'd suggest you put your query on the Narrow Gauge Discussion Board (hope that's OK to write here) as several readers of that forum have had first-hand experiences with Thomas appearances and can fill you in much better than I can.
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