As with most things in 4e, it depends on the power and how it's presented on the item in question.
The important keywords in this particular power are "close" and "burst." It's not a weapon or implement attack, so those bonuses don't apply, nor do enhancement bonuses. However, the +4 basically accounts for those two things (a +2 proficiency weapon with a +2 enhancement bonus, or if viewed as equivalent to an implement attack, a +4 implement, which, given the level of the power, is probably closer to reality).
However, if you have things that enhance the to-hit or damage of "close" or "burst" powers though, then you can use those to enhance this attack. Though in this case, since the power doesn't do damage, damage modifiers are irrelevant.
In the event some other item granted you a melee or ranged attack, then things that affect melee or ranged attacks would be in play, though do be aware that some things require weapon attacks and some magic item powers simply grant "melee" or "ranged" attacks instead of "melee weapon" or "ranged weapon" attacks.