A lot of companies still use irc for intrabusiness communication, though Slack is becoming increasingly popular. I've worked for several startups that conducted business in an official private irc channel. It's especially useful for communicating with remote workers.
Interestingly, Twitch uses irc in its backend to power all of the realtime chat that accompanies its streams.
Interestingly, Twitch uses irc in its backend to power all of the realtime chat that accompanies its streams.