The compedium says that traits are active when " trait modifies the normal procedure for playing that card or another card".
So the question is: is Ivor XP cost modified when he is in boot hill or discard pile, depending on number of aboms in play? In other words is cost reduction a type of modification that is always active?
For example it matters for Soul Cage / Ivor XP interaction, with 5 abominations in play/BH I would need only cheating 3ok, to be able to use Soul Cage to bring him into play.