content: It's most likely only on the end user's side and deals with the efficiency of compression/decompression of data on that side only.  Google wouldn't have any control over what other content delivery systems from various places like Level 3 sends over the broadband connection to users.  So it won't save any data usage over a mobile phone except when it caches the data and when the user sends data back to the server (which will use the better compression).