these numbers could be all purely modern from the mussolini times, as he forced 225000 sicilians into the then italian area of slovenia and croatia, after WWII , these areas where given to yugoslavia and then in the 90s the "italian" populace preferred the more liberated slovenians than the croats ( as well as some returning to italy to migrate OS)
In regards to taurisci and carni, they are both gaulish tribes moving via switzerland through austria. If they are taurisci then there fellow tribal people in Piedmont ( Taurini) would have the same/similar Hg numbers
i think that most people who have settled during ww2 were pushed out after liberation. In fact, also many people (Germans and Italians) who lived in areas before ww2 and were of German and italian origin and were collaborating with occupation troops. So I do not think this is imprint of ww2 settlers.
Taurini lived in north most Italy which is very close to L21 zone if not in it... note that Maciamo's map is approximation and not extremely precise and that Taurini were probably pushed to north and west in initial process of spreading Roman empire..also we do not know whether Taurini were of same genetic origin as Taurisci...they might have just belonged to the same culture.. not to mention that genetic structure of north italy was also heavily changed in times of fall of Roman empire when many germanic tribes pushed out many previous inhabitants and settled there
and if you look other branch of R1b that some people here also consider Celtic (S28) - it spans much much more south than any known position of Celtic people...it matches more with east Germanic settlements..
note that Boii didnot stay in Italy they moved out
so Celtic genetic in Italy can be expected only in north most area (if they didnot move more north and west as they probably did during initial expansion of Roman empire) which matches L21 spread... so L21 matches all last Celt settled area fairly well, while S-28 doesnot
as for north Sicily it could have been settled during Roman empire...Roman empire would typically have army that origin from one part of empire in far distant parts of it... in that way soldiers were not able to rebel locally based on nationality, and would also prevent that army has compassion for local rebels....... and since Sicily is relatively small area, this could have left imprint of around 5%...
or e.g. it could have been moved there to make Sicily stronger against invasions of Vandals and Alans from north Africa... or might (though that is much less likely) have come with Alans and Vandals... in fact pay attention to R-s28 in north Africa - R-S28 thast i propose to be east germanic and many here consider Celtic can in north Africa easily be imprint of east Germanic Vandals...although there is also a historical mention of Celts also in Africa in much earlier times...