The practice of the Italian benandanti might, with a stretch of the word's meaning, be styled "shamanistic". These were people who claimed that, during the ember days (query: which ember days? there are four sets a year) they fought enemies of the community's crops in their dreams. If a "shaman" is a Siberian religious specialist who goes into a tranced state, there to perform actions on his community's behalf, then I suppost the benandanti could qualify as "shamans" too.
Whether this practice derived from antiquity is a separate question. Christendom was creative enough in its own right, and possessed a tradition of respect for dreams (see the scriptural passages about dreams) that the dream-fight practice could have been arrived at independently of any ancient practice. [Whatever the history of the practice, it collided with the new demonology which started up in the late 1400s. Some practitioners of this new science viewed the benandanti with suspicion. I think it is partly from the records of their investigations that we know about the benandanti at all.]
One historian, Carlo Ginzburg, does try to trace practices like that of the benandanti and of Baltic werewolves to deep antiquity. With what success, I don't know. I still haven't read his book, Ecstasies. In one of his earlier books, The Cheese and the Worms he seemed to try to link a tradition of intellectual inquiry found among Italian peasants in the 15th/16th (I can't remember the dates clearly--sorry) century to ancient paganism. This struck me as unnecessary. There was enough intellectual energy in the thought-world of late-medieval Christianity to account for what Ginzburg described, without trying to forge tenuous links to the remote past.