No, it’s not an April Fools’ Joke (which is what I thought at first reading). “Cosmic-ray muons fall equally across the Earth and always travel at the same speed regardless of what matter they traverse, penetrating even kilometres of rock,” said researcher Hiroyuki Tanaka.
It certainly bypasses any attempts to spoof it or jam it, and it has way better penetration than GPS, but it due to its nature, accuracy is only around 2 m to 25 m right now.