D9.54 says : "A Dug-In AFV is HD to all Direct Fire attacks".
So you need a turret hit to hit it (the colored dr of the Original TH DR must be < the white dr - C3.9).
Plus a +1 DRM (or +2 if already a very small target).
And we would need a handful of scenarios using them.
Hoarding maps and overlays which we find necessary without them finding any actual use reminds me of my accumulating or keeping junk in my cellar "just in case"...
In Encounter at Cornimont, German enter with motorcyles under the sights of the French HMG.
Leaving the motorcycles offboard and moving on foot could be a better option (no Bail out + RF attack if failed PTC/MC).
But the German doesn't lose CVP for not bringing the motorcycles in play.