A talk by Joe Armstrong I watched recently indicated that around 50% of 3G and more than that of 4G infrastructure uses Ericsson technology, specifically with swoftware written in Erlang. He made a joke about 'sweating over every bit' sent over the network and then complaining that all the apps are going crazy with their JSON.
Erlang is mentioned only once in this entire article, and it's in the "See also" section. Nothing in this Wikipedia article supports the claim that Ericsson uses Erlang at all.
I'm sorry I can't find the exact video I saw from Joe, but he's generally quite proud of the reach of Erlang so you'll find him stating the facts about how much of the mobile and telecoms infrastructure it supports in a few of his videos! I hope that helps.
I know that. The last I heard was that Erlang decided to stop developing with Erlang, causing Armstrong and others to leave. I see they've reverses that decision and there are mentions of use at various mobile companies, so that's cool.
erlang was literally developed for telephone switches