Based on the diagram I share, that PTP link is connected from WAN to LAN, same for the other side.
Assuming all the LTEs are down, this link has no way to determine that, because based on that setup this 2 PTP links are always up.
Maybe we’re looking at a wrong solution altogether.
Something has been on my mind so far though, regarding how your 580 comes into the picture.
You mentioned between that you have multiple HD4s with 580. Is this referring to a single location, whereby you have a single Balance 580 connected to a few MAX HD4? Personally though, if you have a setup like this with say 1x 580 and 2x HD4, we’re talking about the possibility of having 8 active LTE connections. A scenario where all the LTE fails only happen in movie in my book.
However, if that’s the case and you want some form of load-balancing to happen between different location, maybe something like the following will suit your need.