Take a look at the Content Examples and the Blueprints_Advanced.umap. I suppose what you are looking for can be accomplished in a similar manner to the 1.2 Automatic Wall example.
From the quick look I took in the Blueprints_advanced level in content examples, no that is not quite what Shadowist was talking about for the Fence_Segment is a static mesh, and Shadowist was/is looking to use BSP brushes for that.
And whilst I have to admit that would be awesome, and very powerful, based on my own limited research online, alas that is not possible.