This is from a press release from the Sci Fi Channel:
From executive producers Ronald D. Moore and David Eick ('Battlestar Galactica'), writer Remi Aubuchon ('24') and NBC Universal Television Studio, this new series is set over a half a century before the events that play out in 'Battlestar Galactica.'
The people of the Twelve Colonies are at peace and living in a society not unlike our own, but where high-technology has changed the lives of virtually everyone for the better. But a startling breakthrough in robotics is about to occur, one that will bring to life the age-old dream of marrying artificial intelligence with a mechanical body to create the first living robot - a Cylon.
Following the lives of two families, the Graystones and the Adamas (the family of William Adama, who will one day become the commander of the 'Battlestar Galactica') 'Caprica' weaves corporate intrigue, techno-action and sexual politics into television's first science fiction family saga.
This will place three series in the same TV dimension; parent show 'Battlestar Galactica' and 'Firefly' being the other two. (For more on why/how 'Firefly' shares the same dimension with 'Galactica', check out Thom Holbrook's excellent "Crossovers & Spinoffs", one of the top links there to the left.)
It would be nice to fill out that particular dimension a bit, so that it's not so void of TV shows. Therefore, as far as I can see, since 'Firefly' is set in the future, and 'Galactica' hasn't reached Earth yet, for the time being I see no reason why it can't share the same dimension as 'The West Wing', 'Mr. Sterling', and 'Smallville'.
I could always be proven wrong later, but that's the wonderful thing about Toobworld - it's always in flux.