The theory is that LinuxICE is an implementation of the OpenICE platform stack. nGhost is a core peice of that platform. This may explain a bit further.
nGhost is technically a desktop. It is *not* an overlay, much like windows front-ends. I believe the netbook-launcher in the ubuntu netbook-remix is a very good comparison. http://wiki.openice.org/index.php/The_nGhost_Project
There are no plugins, nor current plans for satellite radio integration. Just not enough demand yet on the Linux side.
Hope that helps!