Some time ago I stumbled upon a great paper by Hoppe, Lawrence, Sander and Yang. It is about a method to restore antialiasing that has been damaged by nonlinear image processing operations. As I was working on a bilateral mean-shift filter back then which suffered from such artifacting I adopted it in Nuke via Blink Script. In a nutshell this implementation analyzes the antialiased source to estimate the original colors of the edges that were blended together. Based on this information the current pixel coverage is computed and applied to the damaged/unfiltered target image.
If you want more in-depth info about this method check out the paper of Hoppe et al. here! I will try to keep the file linked in this post up-to-date and you can definitely get the latest version on nukepedia.