The files are in the game...I made a thread about it quite a while ago now...the files were in there before the alpha, so this has nothing to do with NDA.
If you use the asset browser and open ArtAEF.sga follow the folder path to data/art/armies/aef/vehicles there you will find a folder labelled m26_pershing as of now it only contains one skin the us_0008_skin for both summer and winter.
Want more proof? Here's a pic of the Archive Viewer looking into the AEF.sga for the live version of COH2.