We can’t verify that. They have a vested interest in lying, and occasionally are barred from disclosing government requests. However, using this as evidence, as I suggested in my previous comment, we can use it to make informed guesses as to what data they can share. They can’t share the content of the message or calls – This is believable and assumed. But they don’t mention anything surrounding the message, such as whom they sent it to (and it is them who receives and sends the messages), when, how big it was, etc. They say they don’t have access to your contact book – This is also very likely true. But that isn’t the same as not being able to provide a social graph, since they know everyone you’ve spoken to, even if they don’t know what you’ve saved about those people on your device. They also don’t mention anything about the connection they might collect that isn’t directly relevant to providing the service, like device info.
Think about the feasibility of interacting with feds in the manner they imply. No extra communication to explain that they can’t provide info they don’t have? Even though they feel the need to communicate that to their customers. Of course this isn’t the extent of the communication, or they’d be in jail. But they’re comfortable spinning narratives. Consider their whole business is dependant on how they react to these requests. Do you think it’s likely their communication of how they handled it is half-truths?
Your client talks to their server, their server talks to your friend’s client. They don’t accept third party apps. The server code is open source, not a secret. But that doesn’t mean it isn’t 99% the open source code, with a few privacy breaking changes. Or that the server software runs exactly as implied, but that that is moot since other software also runs on the same servers and intercepts the data.