Question : Setting up SCR for Exchange 2007

I have a question on setting up SCR.  First off I think it makes sense to explain my environment to see if what I think SCR can really do for me.
2 Exchange 2007 servers.   1 server in the parent domain and 1 server in the child domain.  Servers are in the same Exchange org and are located over a 15mb Wan/site to site vpn.
2 seperate companies.  Both exchange are the primary active exchange server for each company.

1) Can  I implement SCR on both servers to replicate each servers mailbox store.  The documentation talks about a standby server or a cluster server.  In my case both servers would have SCR enabled replicating its data in both directions.  Can this be done?

Answer : Setting up SCR for Exchange 2007

Unfortunately I don't think you're going to be able to do what you want due to one simple requirement of SCR: "Target machines must be in the same Active Directory domain".

I might be able to help you put together an alternate solution, if I knew your goal - is it protection against data loss or automatic failover or?