I've been learning Italian for the last 18 months, and the conversation class is lead by Giovanni, who is from Friuli in the far North, and by Franco who is Sicilian. I can assure you that 'mosca' sounding like 'musca' is well within the limits of the different accents! I have also found plenty of evidence both from Franco, and the excellent "Inspector Montalbano" (BBC4, saturdays) of Greek influences in the former Magna Graecia (southern Italy)
Cheers
Dave