I know this thread is pretty old, but I wanted to share what I think is the current software version.
It appears that for 2015 and 2016 vehicles it is now 16.40-42475606. I do not think it matters what trim level or if you have DC fast charging or not.
If you enter your VIN number on tis2web.service.gm.com under A11 radio, USB file transfer, UF7, 1CZ48, you will see the software version for the USB memory stick which is uploaded to the radio. Either 42475606 for 2015 and 2016, or 95281509 for 2014.
The software update process is to install the update from a USB memory stick, then update the "calibrations" afterward. I was able to update my vehicle myself, but I had to purchase a scantool (VXDIAG VCX NANO for GDS2) and I had to purchase a 2-day subscription to http://www.acdelcotds.com
to access the updates. I did this because the car dealer was unable to do this for some reason and my car is out of warranty. It did take me a while to figure all this out, and it is kind of a difficult and buggy process.
One thing I learned is if you get an "invalid SMD file" message when trying to install the USB memory stick, you will need to set the car clock to 00:00 01/01/2011 first then try again. I could not get my date to stay changed, it kept changing back to the current date, until I toggled the automatic clock sync setting on then off again. Also, since my vehicle is a 2014 I had to fool it with a 2015 or 2016 VIN to get to 16.40. The newest version I could download with my VIN was 14.7. I think the radios which shipped on the cars had newer versions, mine did. Looks like they dropped update support for the 2014's...
After I updated everything, I was able to use development mode to enable Mirror Link by copying the Russian ClientAppInfo.bin file posted on sourceforge.net/p/mylink-unlock-project . I have not been able to test the Mirror Link, due to my old Samsung S4 being incapable...but the icon is there now.