Possible Bug with Tier 2 Towers and Fog of War

When you move up to the T2 towers, you get a shield. But if you take notice, you'll see a white little whispy fog animation right as you start getting the shield. In one of my replays that I was rewatching, I noticed that even though I was in my opponent's fog of war, it showed the shield animation as soon as I approached my T2 turret (It could have simply have just been the replay showing animation).

I was playing Sona and baiting the Elise to dive my Lucian who was under the T2 tower. The time in the replay that shows it is at 18:56. If you switch it to Red fog of war, you can see the animation before I appear in vision.

Here is my replay: http://www.replay.gg/?r=NA1&id=1948997550&key=kQFkrOHLfjpX8AJE5dztXCaYw1%2Bqlod9

Could one of you kind players verify if this is a replay bug, fog of war bug, or an intended result?

Thank you.