As per IO, pg 75,
All to-hit modifiers imposed on an EI-equipped unit making
weapon attacks through woods, jungle, or smoke hexes are
reduced by 1 point (to a minimum modifier of +1) per hex.
Does the "to a minimum modifier of +1" apply to each hex, or to the total? If the minimum modifier is applied per hex, then the only time EI would offer a TH mod is when shooting through heavy woods, jungle or smoke.