I am not sure what study is presently being used by Team X to beat Team S over the head with, but from this this Nature
article (link), I followed the trail to this
(link), which in turn means you have to click on a download link to see the paper. Looks like it needs peer review, so, am sure there will be discussion about that angle as well.
View attachment 119782
By my seat of the pants observations of real life, it seems to me that if masks didn't help reduce transmission of aerosol droplets which may contain germs, they wouldn't be used during any routine surgery. Whether or not this observation applies to viral pandemics, yeah, I don't know 100% if I can say, but for me any increase above 0 % with minimal cost to me sounds worthwhile.