Can Circles users spy on mobile users from any country, or only handsets from the same country/network? If I disable roaming on my mobile account, will my mobi

Can Circles users spy on mobile users from any country, or only handsets from the same country/network? If I disable roaming on my mobile account, will my mobile service provider reject intercept requests? Why is authentication optional in 4G and 5G? Do SS7 network participants suffer fraud? For example, a small telco in a developing country could charge random foreign customers for international calls that never occurred.