Well, indeed tubut is right about the location. Solvay is a huge chemical company of Belgian origin, still active worldwide, which created ex nihilo a plant and a village with it in the Piombino area, on Tuscan coast. (BTW, it also polluted the sea and the people around for 50 years in an inbelievable way).
Yet, while the SAV acronym related to the Venice-Padova motorways seems to me unrelated, I'm not convinced that the link found for a company based in Cuneo could be relevant for the period implied by those busses style and construction either. Moreover, that SAV RENTS busses, it doesn't organize regular lines.
Such companies running pretty local lines have been numerous over time.
As for the identification of the chassis, the lookalike design of the coachwork say pretty little about that. It's a matter of trends, patents, aerodynamics as intended at the moment etc., while the various existing chassis were similar enough as to receive the bodies at the will of the customer.
The badge would tell, and it doesn't look much Alfa to me. Viberti's chrome script, albeit not very visible here, is probable instead.
Recently, I saved this (watermarked) picture from an eBay listing. It's Viberti, as the script reads, and the caption here says it's indeed an Alfa 500 chassis.
But notice the difference of headlights: the EIAR design is a futuristic '30s design, when even on sporstcars the headlighs were stilla apart, as they are on the other bus, and still differtently on mine here. The faired headlights of the other one look more 40s-50s to me, which is more a fashion of the time and doesn't compare with the Revelli design as for audace. Note also the difference of windscreen, which could be a hint to different driver positions, and even the length of the wheelbase doesn't seem the same to me.
I know there is a picture of yet another similar looking bus in the "Storia dell'autobus italiano" book, but I don't have it on my shelf, so I can't say the chassis.