The particular solution this company is implementing is unorthodox, but you usually can not expect that your company email account is a private medium.
When you are using a company mailserver, then all mails you send and receive will be stored on it in clear text. That means if management feels that they need to read your work email, then it is usually possible for them to do that. A more savvy mailserver administrator would be able to silently forward all emails to that ceo_bcc mailbox automatically without requiring any actions from the end-user.
Having the end-users do this manually instead of implementing an automatic solution is dangerous, though. People will forget that from time to time. If the intention behind this policy are benevolent, then it might result in the management not being aware of something they should be, leading to wrong decisions being made. If the intention is malevolent, then non-BCCed mails could be used as a pretext to sanction someone.
So what do you discuss with the CEO? Tell them to ask the IT department to set up an automatic forwarding rule so you no longer need to do this manually.