No. Pairing another bluetooth device will not let you make calls through your infotainment. It will still let you hear the caller, but they will not be able hear you.
However, you could pair your phone with a sena, scala, or other Bluetooth headset and complete calls thought the headset. So, the call sounds wouldn't come through the Harley speakers at all. You can do this by changing the settings on infotainment so that it pairs with your phone for media pairing- but not for communications.... After one call from my Mom while riding, I realized I wouldn't want my calls bumping through the Harley speakers anyway.
Or, you get the Harley hard wired headset and go that route.
Good point with your mother calling and that conversation coming through for all the world to hear My wife calling might be something I want to avoid as well!
Until I purchase a bluetooth device and attempt your statement above, I believe what you described is what I am trying to do. Thanks for the tip and humor!