Looking through what's been posted it seems like the following is true:
Egypt in STRONG against: Gem, Treasure, Ice Cream
Egypt is WEAK against: Nature, Water
It seems neutral to other standard (non-event) elements so far.
The other event-only elements that still need to be tested are: Xmas, Valentine, Shamrock, Cosmic, Music, Egypt, and Living Wood (not really an 'event-only' element, but it's a unique one).