Hi James, IIRC there are separate folders for airbase files in ETO. The dds, and mos files for the ACC airbases are in there. Not in the traditional fxtextures or assets files.
I tend to reorganise the files when I install ETO so that all the airbase dds files are in a sub-folder. This eliminates the potential for duplicate .dds files (also a reason for organising the aircraft/shared folder dds files as well). There is also the odd airbase spelled incorrectly, then correctly leading to unwanted testures.