I do not know if this will help you, but it is my experience with the XMD1000.
The unit appears to update the channels live exactly like the XM Xpress (stand alone unit) reciever in my other car, if not faster and independantly of one another. The channels update track info both on the current channel and the ones listed on the screen at the time. I have about 10 visible at any given time with my setup. this is very handy and I use it to see what I want to listen to next based on what is playing on other channels.