Probably not, but again depends on the circumstances. If, say, the company normally used Slack but for a single project all communication was strictly off-the-r

Probably not, but again depends on the circumstances. If, say, the company normally used Slack but for a single project all communication was strictly off-the-record on something like Wickr. And that project just happened to be involved in an espionage lawsuit. And someone testified that they used the secret app specifically to avoid future litigation...