An email correspondent pointed out a 2011 paper to me, "Structural diversity of bacterial flagellar motors," published by the European Molecular Biology Organization. The paper looks at bacterial flagella from a wide phylogenetic distribution using "electron cryotomography" — a pretty new technique that they say allows them to get greater detail more easily.
They write in the abstract that "While a conserved structural core was observed in all 11 bacteria imaged, surprisingly novel and divergent structures as well as different symmetries were observed surrounding the core." To my reading, though, the more striking fact is the first part of their sentence — that all flagella had the same necessary components in the same relative spatial relationships.
The second part of the sentence, that there are differences too, is interesting. But beyond showing somewhat altered shapes and unidentified regions of photographic density, the role of the novelties are unknown.
It seems to me the bigger story is the finding of a strongly conserved core occasionally tricked out with a few decorations. The authors mildly hint that there are renegades out there who would use the flagellum for nefarious purposes ("…the occasional misrepresentation of the motor as an invariant, ideal machine"), which probably leads them to emphasize the novelty. But this study should offer little comfort to Darwinists.