It may be a while as we're going to try going Softphone as plan A, then 6920 BT as plan B. I will update this thread if and when we go w/ B. The person won't onboard for a few more weeks as well.
From the 6920 data sheet document "MobileLink is enabled with the addition of the optional USB Bluetooth dongle, allowing connection of the user’s mobile phone to access many of the features of their mobile phone from their desk phone, making the MiVoice 6920 one of the most advanced general purpose IP desktop phones available today" - we'll see... I've also heard that other documents only list a 6970 speaker working with a 6920 via bluetooth.
Regards