One of the things I tell customers about often is the advantage of the portal concept as enabled by the Tivoli Enterprise Portal. If the necessary data is in the portal, then you can use it to solve a problem, regardless of which monitoring agent it may come from. Here's a good example of what I'm talking about.
If you run both OMEGAMON XE for Mainframe Networks and OMEGAMON XE for IMS on z/OS, you can use custom workspaces, filtering, and situations to monitor the connections associated with the IMS Connect Address Space using the OMEGAMON XE for Mainframe Networks. Here is a link to a white paper that goes into detail on how to do this.