No, this approach cannot send encrypted messages as it is only firing events (not listening to your chat to receive encryption keys - you wouldn't want the server to do this, right?). However, you can add it to encrypted chats, it will then send a plaintext message. Assuming that the event would be public anyway, this should not matter too much.
Encryption could only be achieved by writing your custom bot that gets a webhook (e.g. via HTTPS) and sends the encrypted message for you.
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