Well, I was experimenting with the Infotainment System on my SVTC over the past couple of days and have some observations. Please keep in mind that these things may or may not happen the same way on your. If you can confirm or refute anything here then please do. I won't take offense! I was getting a little brain fried trying to recreate some of this stuff and I may not have explained it very well...
There is a volume screen in settings that is accessed by going to the Audio Settings menu, and then Volume. In there you'll find the volume settings for Media, Phone, Intercom, and CB. The volume switch on the handlebar changes the Media value by the way.
I had Media set to zero because I didn't want any radio sound, but I didn't get sound from anything (such as the intercom.) I was assuming that the Intercom volume was controlled by the value set in the settings screen. If I set Media to 1 then I could faintly hear the radio (as you would expect) but the Intercom volume came in at the value set in the settings screen. If I set Media to 2 then Intercom also went up. It acted as if the Intercom volume was being set to its starting volume (from the settings screen) PLUS the Media value.
The manual leads you to believe that there is a separation of volume function between Phone, Intercom, CB, and the other audio sources.
Moving on...
The rider PTT is just that, pull it in and the mic is enabled, release it and it is disabled.
The passenger PTT doesn't work the same way. You push it and release it and the mics are on, push it and release it again and the mics are off.
If you only had the intercom enabled (and not the CB) then this might be OK. The passenger could push their PTT button to lock the mics ON and you could just chat back and forth without having to push PTT switches. The problem is when you have the CB enabled. The manual states that the CB gets priority of the mic, so if the mics were locked on by the passenger PTT switch you would be constantly broadcasting on the CB. Not good.
I did find that if the mics are locked on by the passenger PTT switch the rider can pull on their PTT switch for a second or two and then release and that will disengage the mics.
I played a bit with the VOX setting and found that it functioned the same as the rider PTT switch and not like the passenger PTT switch (i.e. the mics would engage while talking was going on and then disengage when the talking stopped.)
I came across a couple other odd things that happened but I'm not even sure I can explain them in a clear fashion until I work with them some more...