I think it would be possible to have long-distance magical communication without having a traditional rp "network" that's available by default to all characters. There could even be a variety of long-distance communication methods! People could share enchanted diaries with their friends to chat by text, or they could use magic to be virtually present in another place... there are a lot of ways to overcome problems of distance without having a typical "network comm." Open network posts are convenient as a fallback method for getting initial CR or to scrape by with some last-minute AC , I guess, but in an AU game you can manipulate the character's backstory to give them instant CR.