I'm almost certain that analysis of multiple stereo tracks works fine (up to 4 stereo signals). Plugin has 4 stereo inputs, so in order to analyze multiple tracks in the same time you have to route each stereo track to each stereo input of this plugin. The easiest way (probably) is to create separate track (i.e. metering track), add plugin as an insert on this metering track, send each stereo track (that you are going to analyze) to metering track but you have to route to different inputs (i.e. input 1-2, 3-4, 5-6, 7-8). I'm not very familiar with Cubase but I think something like this should not be impossible to do.
In the future I'm planning to implement some magic "global" mode. When enabled all instances of plugin inside DAW will draw channels from all other instances automatically. But that will need some more thought.