An event can still be situationally, or cosmically ironic even if it's not in fiction. if you really want it to be a property of communication, then think of the communication as being between the universe, or God and the subject.

More importantly, English is defined by common usage, and the usage of irony in describing an unexpected combination of real events has been common for hundreds of years. I believe this probably comes from people's common belief in fate, or that their lives are part of some broader story. Under this mindset, it makes perfect sense to use terms from literature to describe phenomena of life. And your insistence that irony is a property of communication is satisfied.

Words have multiple senses, and the ones from common usage are just as valid as the ones from academic usage, though they may be harder to pin down.