Temporary Fence

[BretMan]

The first part of your post is the same as I've always understood: A fence lying on ground effectively extends live-ball area and a fielder standing on that collapsed fence is regarded as being in a live-ball area. And, in fact, this comes straight from the ASA Rules Supplement.

The second part, about the base of the fence moving, is a new one on me. With just about any temporary fencing I can imagine, I think that the base will be moved if the fence is knocked over. I've never seen this interpretation in print, nor seen it brought up in the many discussions on "collapsed fences" over the years.