Counterspelling Magic Items

[Galtrug]

In the event that a magic item simulates the effects of a spell, would the use of the magic item be counterspellable? Would the answer to that question vary depending on if the item is a spell completion, spell trigger, command word, or use-activated item? While I'm inclined to think one could counterspell some uses of items, the idea of someone counterspelling a potion strikes me as just plain odd.

[dragonhunterq]

counterspelling

You can only counterspell a spell being cast, not the activation of a magic item.