The original thread (in Russian) is here. Actually the original thread is about several tools to works with different images for different phones. But we will talk only about Moto X.
The guide will describe how to extract all files from system partition from stock firmware. The tools works under Windows (I personally tested it on Win 7).
If you unzip any stock firmware (for instance ROGERS-CA_GHOST_KXA20.16-1.26_cid14_CFC_1FF.xml.zip) you will find one file, which represents system partition: system.img.
To extract all files from system.img please do:
1. Download ImgExtractor_1_3_4.rar and extract it.
2. Create directory System in the folder where system.img is located;
3. Copy ImgExtractor.exe into the folder where system.img is located;
4. Run CMD and "cd" to the folder where system.img is located
5. In CMD run the following: ImgExtractor system.img System
After ImgExtractor finished you will have all system files and folders in System directory.
PS. ImgExtractor also can extract modem firmware (NON-HLOS.bin)