Hi Mark, no MoI does not have exactly the same thing as a Rhino group yet, but it is something that I do plan on working on for MoI v3.

In the meantime though, there is a mechanism called "object names" that you can use - if you give the same name to several objects then you can select them all together by using the scene browser entry for that item - click on the name text in the scene browser to do selection.

Some more info on the scene browser here:
http://moi3d.com/2.0/docs/moi_command_reference11.htm#scenebrowser

- Michael