Below is a link to an article about the work being done to keep European C-17s both up to date and in good condition for continued operations. Although the mod and maintenance packages vary, both the RAF and RAAF (and many other non US owned C-17s) send their C-17s to the same facility for modification and maintenance work. At least one forum member works in San Antonio and is heavily engaged in this work.
First heavy maintenance cycle complete for SAC C-17s