There is quite substantial literature on the Open Access citation advantage. However but that focuses exclusively on sharing journal articles. I wonder if there is any additional effect by sharing early versions of papers, e.g. as preprint or working paper. Of course you would need to look at citations to the various versions (preprint plus regular journal article) and add them up. Do you have any leads on evidence or research into this?
I do know there is evidence for the High Energy Physics Field (https://arxiv.org/ftp/arxiv/papers/0906/0906.5418.pdf), but wonder if there is evidence from other fields as well.