According to posts on Digitalspy, Setanta have secured home rights to the following teams:
Due to the way rights are sold in Italy, each team sells their rights to an intermediate company, who in turn sell on the collective rights. All the "big teams" have sold their rights to one company, and the teams above have sold theirs to a different one. Although this will pretty much guarantee Setanta that the likes of AC Milan, Inter Milan or Juventus will be on most weekends against one of these teams, it's a shame that if this is true things like the Milan or Rome derbies won't be live in the UK. However, as these rights can probably be picked up quite quickly, and as Serie A has not proved to be a ratings winner in the past, you can't blame Setanta for hedging their bets.
However, this information was found on the Setanta Australia website, and as Setanta have yet to update their EPG with details of live matches for this weekend, it appears to be still in negoations.
Bet365 are showing a selection of live matches for this weekend, including the "big teams" home matches, so that could be a way to make up for matches not screened on Setanta.