A caster can use any spell trigger item of a spell that appears on his spell list, and any spell completion item for a spell on his list that he can make a CL check for. An archivist's spell list is made of of every divine spell. The only difference between a cleric spell and a non-cleric spell is that an archivist doesn't automatically add non-cleric divine spells to his spellbook, he has to scribe them from scrolls. They are still on his spell list though.