where i am from, such policing is illegal. germany has a different approach to freedom of speech. no institution is allowed to even monitor, let alone censor private conversations (that includes overhearing something). private conversations at work are private and legally protected. the only time when a company can interfere is if the manner of communication (not the content) is disruptive. and getting fired for being disruptive in most cases leads to a lawsuit from the employee against the company, and so courts will decide if there actually was a disruption, and if it was bad enough to warrant dismissal.