We once had this problem (I don't know if this is similar to your's):
We wanted to connect to multi databases, which had same database  schema. This is possible to switch the actual database connection, the hibernate  will not care about it.

Have a look at:
http://blog.exadel.com/?p=16
forum.springframework.org/showthread.php?t=11355
forum.springframework.org/showthread.php?t=10501