It looks like this was asked 2-3 years ago, with no answer at that time.
As an MEP firm, we screen the architectural background. I have that working fine in Revit using halftone overrides, etc.
From what I've found so-far, there is no way to export the Revit halftone property. I have tried exporting with overrides byentity and new layers for overrides. I even found a blog post (not sure how old) that states it cannot be done.
If you have a solution, or can confirm that it just cannot be done, please let me know.