Have the results of the USAF's $AVE program research been implemented?
The C-17 has a special autopilot system including a component called the MILCAS-FR formation flying system by Honeywell and here is a link a sales brochure.

My military flight time was not in a C-17 but in my opinion once the precise formation locations were determined that achieve the fuel savings in the article it would be a simple decision to use them on any given formation flight based on the tactical situation.  The requirements of each mission would drive that decision.