So the title of this post sounds kind of crazy, and you may be asking yourself, WHY???
Well, internally we have two networks and two separate forests connected over a gigabit fiber link. These locations are in two separate buildings in the city. One is in our office, and one is in our hosted data center.
Without diving too deep into our network setup, the point is, we have a SQL server in our office that is currently being decommissioned, and it holds the OCS R2 Enterprise Pool backend. In our data center, we have a very nice SQL 2008 server to move all the databases to.
To sum things up, this does indeed work, at least in our situation. It is important to note that it is not supported nor recommended as I have only tested basic functionality, and done no performance testing. Also, we have a full two way trust between these forests, so permissions were not an issue.
In the end, we decided not to do it because we rely too heavily on OCS as our complete UC platform, and did not want to risk any performance issues.
If this is something you absolutely must do, it does in fact work.