they are both natural, but they are used for separate purposes.
1) I was informed our company has hired a new guy: you say this if you are arguing with someone or complaining to someone, or analyzing something, and you are saying where your point of view came from, and that it may not be true. Also, be aware, when you when you use the word "I was informed" instead of "I heard" it means that you found out something in a way that is not casual, or that you do not think about in a casual way. The use of the word "informed" is formal and the use of the word "guy" is casual, so the sentence shows that you feel in control of the information, even though you are speaking in a casual way, sort of like when a policeman says "at approximately 13:45 we apprehended the m#[email protected]
2) I have been informed our company has hired a new guy: you say this if this has just now happened, and that the information is true and the purpose is to inform other people as well.