When I worked for an international bank during the late 90s and early 2000s they had a global IRC network on their internal WAN.

It was heavily used by all staff, which was fairly unique compared to the other banks at the time.

Over time the bank developed their own dedicated client for it, and added extensions to the servers for audit logging and username/realname enforcement, and then eventually spun the department developing the tech off into it's own startup company that then sold the product to other banks and companies. That spin off company is still around selling online collaboration software.

Qualcomm has such an IRC server. I interned there and used IRC to chat with the other interns even though most of the full-time employees used Skype for business.

I'm sure most large, old tech companies have at least one IRC server that someone's forgotten to shut down. And my employer also uses Jabber, but I'm pretty sure it's just because it allows them to have complete control over the relay and client.

At least they are using something which is an open standard, that's a good thing