I answered the questions myself.
In our Spring loaded HIbernate I
1) Removed the Naming Strategy and hardcoded the table prefixes.
2) I added to the SessionFactory the following property (which is schema name dot )
3) I created the schema in our postgres database.
And it worked great!
this seems to be a quite frequently asked question - maybe you could add your solution to the FAQ? (https://www.jboss.org/community/docs/DOC-13216)
Also, if you have a patch on Envers that would allow it (maybe through a configurable property?), maybe you could contribute it? :)