The releng tools provide two actions for updating copyrights, "Fix Copyrights" and "Eclipse/IBM Fix Copyrights". According to John Arthorne, the two are doing almost the same thing, except that the latter only updates the copyright if the last commit comment did not include the word "copyright". This avoids a potential ripple effect.
Unfortunately, I ran into https://bugs.eclipse.org/bugs/show_bug.cgi?id=276255 and will have to run the tool again, using the proposed bugfix. This means that I won't make it for tonight's build, and that the updated copyrights will have to go into RC3.