Arcane Surge does not affect items equally.

[adeptusforgeceo]

Silence Wave is not affected at all.
Reactive Barrier is not affected at all.
Cold Front/Arctic Blast are not affected at all.
Phantom Strike is not affected at all.
Decay bugs out, causing it to show the cast indicator from the "increased" range and allows you to "cast" it, but does nothing and doesn't put the item on cooldown.
Knockdown gains the extra range/duration as normal.

I didn't test anymore items because those are the ones that immediately came to mind, but I imagine there's a lot of other items with inconsistent effects.

 

[Arman]

Is it intended to benefit items in the first place? It says it buffs your next ability, not that it gives you those stats directly to be used on anything (though the wiki seems to imply it is a buff). According to the wiki it should not affect items at all, and based on your testing it seems to mostly follow that.

 

[adeptusforgeceo]

Either way its a bug, because its affecting some items and not others.

Fun Fact: a lot of things count as abilities under the hood. Walker Slam counts as an ability, and can be silenced by Mina Ult for instance.