[Mobhack]

If you make the ammo trucks expensive then you can run into the problem of artillery overload points as they are classed as artillery units (because they are a force multiplier for humans, but not the AI, so this is deliberate to penalise human players for their use).

If the scenario designer wants some expensive trucks to guard - then best to use heavy trucks and set their points high. If he wants to make then explodable, then he can give them an explosive weapon (see the suicide trucks in the PLO(?) OOB) - but then the AI may use them as suicide trucks of course, so that may not be the best idea if they are on the AI side.