Some items and effects bypass/ignore server property pvp setting, blood contract, vanilla teams and FTB Teams.
Items / spells tested:
The Magic Ray Book from the "Companions!" mod (does full damage)
Cyroheart bow from the "Too Many Bows" mod (no damage, slow effect applies)(misspelled in this pack?)
Poison Arrow spell from the "Iron's Spells 'n Spellbooks" mod (no impact damage, poison cloud applies damage and debuff)
I am still early game and have not had a chance to test with other items and effects, so unsure how widespread of an issue this is, but I could not find a resolution and assume it is unintended.