Yeah, I was taken back by the heavy steel gate that Michonne climbed over. How was that gate there? It was also annoying that it took her like 45 seconds to pull free and climb over.
The chain-link dead end made more sense. Though I don't know why, when you were on the dumpster, you wouldn't just climb across the fence to the roof. I saw the barbed wire on top of the fence, but the roof seemed pretty clear.