Thank you for your patience thus far. I finally got around to investigating that siren. From my evidence, I can conclude that it was probably not a siren. The Jefferson Fire Department does not claim to have owned it. I have not checked with Sparta and I will be doing that soon. However, The pole mount looks very similar to a pole expansion which is when a pole is too short and they need to add to the length of it. This can also be observed in other townships around New Jersey like Bloomingdale, NJ. This is usually used to raise powerlines above a certain height. From what I’ve seen there is a second pole not much deeper in the woods, that looks to be a pole that was connected to it. It could still be a siren but it most likely is not. With all of the other evidence that I’ve gathered, I personally can come to the conclusion that this was most likely not a siren. It was probably a power transmission line for that trail.
Thanks for your patience and I will still be looking into this.