Skylinerw | @Alphabot6 - Detecting Worldborder Size @Skylinerw | Uploaded 10 years ago | Updated 13 hours ago
Commands: http://pastebin.com/XEbBuXB0

EXPLANATION:

The "/worldborder get" command will return the width of the border in blocks to the initiator. This doesn't do anything further without the aid of CommandStats. Setting the "QueryResult" stat will take that output and set a players' score. Using that, we can set the score of a fake player to the size of the worldborder, and then test for that size.