CSLA .NET makes it easy to separate your data access logic (DAL) from the rest of your application.
Because you should use CSLA to create business objects that map to the problem domain, not the database shape, your DAL should be concerned with accessing the database and mapping the data into the business objects as necessary.
If you have two different database schemas then you'll probably have two DAL implementations, both of which access the databases and map the data into the exactly same business types.
The Using CSLA 4: Data Access ebook covers this pretty extensively, and the ProjectTracker sample (version 4.0 and higher) uses an abstract DAL that demonstrates the concept as well.