First it's good to have an understanding of View Disciplines and how all six differ from each other. You can separate the View Disciplines into three different groups:
Coordination, Architectural
Structural
Mechanical, Electrical, Plumbing
All three MEP's work the same. They apply a halftone to non-MEP categories including Model Lines. Detail Lines do not show as halftone in MEP View Disciplines. But, this automatic halftone feature is actually a global setting shown here:
This checkbox is the magic key:
This is what controls the "automatic halftone" feature in the MEP View Disciplines. Turn this off and you can still apply Halftone to your Links via the V/G Revit Links Tab. So there's a tradeoff here and you'll have to try this global setting to see how you prefer your environment to be set up. Hope this helps.
-TZ