PRN of course is well known and a big player in digital out of home in the US.
It’s actually owned by Thomson SA, who also own Technicolor and Convergent Media (their other OOH business unit in the USA).
See http://www.thomson.net 
Thomson’s only activity at present in Europe is in Poland, where they have a contract with Carrefour.
They do, I believe have major roll outs planned in China and Brazil.
Thomson’s operations outside the USA are run from Paris, France.