@evan my clients have a lot of internal comms tools, mainly Slack & Teams right now. But it's ever changing.
Vanilla Slack could be easily replaced by an ActivityPub system, but I don't think Mastodon is up to the task right now.
I can't imagine relocating to their public Mastodon instance, if they had one. Their sr. management & board is evil and entirely untrustworthy and that's not changing any time soon.