I was under the impression that Don Tommasino had taken over Cicco's power base once he and Vito had killed the elderly Don. But, I suppose there would have been other Dons in Sicily at the time.
I think he had his own power base and was the Corleone's "go to" guy in Sicily.
"Io sono stanco, sono imbigliato, and I wan't everyone here to know, there ain't gonna be no trouble from me..Don Corleone..Cicc' a port!"
