Originally Posted by Dovster
I have done that repeatedly with both Avis and Hertz but with no luck.

I guess because they are in Italy where variable road tolls apply. Can't really blame them for not increasing their costs by paying for a foreign tax. Rent in Switzerland and you get a Swiss sticker.
I haven't rented in Austria since they introduced a simlar system to the Swiss, but I imagine the Austrian renters would include the sticker.