Comment 23 for bug 895468

EMP works like this 2:

Immunity
Use ImmuneToEMP=yes to create a unit that is immune to EMP. There is no way to paralyse this unit at all.

If the unit is Veteran/Elite and there's the EMPIMMUNE veteran/elite ability, the unit counts as immune, too, and can never be emp'd.

Use AffectsAllies=no on the EMP warhead to make units immune to own and allied EMP fire. Likewise, use AffectsEnemies to create positive EMP weapons that really should not help the enemy.

Otherwise, units having at least one EMP weapon can use TypeImmune=yes to protect themself from EMPs fired by the same owner. For example: two Mobile EMPs could not blow each other's lights out.

If ImmuneToEMP=no, this unit may be paralysed (if no other tags already prevent this). It does not matter what type this unit is of.

Default values
ImmuneToEMP infers its default value by whether a type of unit isn't prone to EMP effects. These default values can be overridden and are just used if ImmuneToEMP is not defined for that type.

Buildings are prone to EMP if they have at least one of the following tags set:
Radar, SuperWeapon, SuperWeapon2, UndeploysInto, PowersUnit, Sensors, LaserFencePost, or GapGenerator. If they don't, they are prone if and only if they consume Power and need it to function (Power