When I use the Vue tool bar in XSI, Vue is not running.  However, it does load Vue when I choose any of the toolbar options in XSI.  In fact, XSI tells me that it is going to rearrange my interface in XSI to match what Vue has.  I see no visible change, and the Mental Ray rendering engine works in XSI, but there are some minor changes.

That said, when I am using xsi to make a terrain in Vue, even though I get the vue splash screen, vue is not loaded and not accessible in my task bar.  It can only be accessed through xsi.