Yes sir, that is the OS I was referring to in post #3. There were no 4L80s that used that OS.
Given that, you have two primary options. Use the Frost adapter harness (which uses a 4L60/70 tune to operate a 4L80), and configure the 2007 TBSS 4L70 TCM tune to work correctly with the 4L80 (not your fault - you don't have access to some of the necessary parameters).
Or, transition to 2008 TBSS ECM & TCM tunes.
If memory serves ScarabEpic22 has ran his 2008 TBSS on 2007 TBSS tunes, and the other modules on the CAN Bus were OK with this.
I build Hot Rods and Customs, so I never have to be overly concerned about communication with additional modules (beyond the ECM & TCM). However, module communications will be at the heart of your issue.
A 2007 Silverado 4L80 TCM calibration will not communicate with your 2007 TBSS ECM - so that is out. A 2007 TBSS ECM will communicate with some earlier TCM calibrations, but a 2008 TBSS ECM will not. This means that the communication protocols are different between 2007 & 2008 TBSS ECMs.
Where I am going with all of this ? I you elect to try a 2008+ 4L80 TCM calibration, odds are you will need to use a 2008 TBSS ECM calibration, to establish proper communications.