Anyone...
...that has do deal with installing Telco lines will tell you what an ustter cluster-fuck of mis-matched regulations and exclusivity by the back door T&C's there are.
Want to drop a circuit into Country Y no problem, pick your carrier and away you go. However country Z, you have to chose an approved Telco provider, of which there is one, which so happens to be pretty much government owned. Want to send "spoofed"* caller id, no problem in country A, but nightmare in country B. And so on and so on.
*spoofed caller ID are actually a very good thing for many. You may want to send the main company number, not the default circuit number, which may work at only certain points in time.