My opinion is that it should be just like when an enemy builds a structure, produces a new unit, and so on. Since we aren't notified of those events, I don't believe we need to be notified of oil events.
However, on the power topic, I miss the "power resource" audio in 2.3b4 when our own truck drives by an untapped power resource. I know this is because all the oil is already revealed on the map. But the audio was useful when you drove a truck right past an untapped power resource to remind you to build a derrick.
It also seems that the AI never picks up oil drums, is that correct?
In a game with such a complex visibility model, it makes no sense to announce something like oil collection. It defeats the whole purpose of the visibility model: that you need to scout around to learn what your opponent's doing. Why should oil collection be such a specific and arbitrary exception?
Unless someone has reasons otherwise, I see no reason why this should even be in question.