In SCOM2007R2 you could multihome an agent to different management groups but it was quite the hassle as there was no option in the management console to control this feature. In SCOM 2012 this has changed by including the Operations Manager Agent Application
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Read the complete post at http://scug.be/blogs/dieter/archive/2012/01/16/scom-2012-what-s-new-agent-config-in-scom2012.aspx