Business landline - Call forward on busy

Can anyone confirm if call forward only on busy is supported on the business landlines, even if an 'add-on' needs to be purchased?

Customer support has told me 'no', but I want to reach out to the community to make sure that this is the case. It seems pretty odd that such basic functionality is not offered.

As documented here, this is supported on mobiles. I can't find any reference to landline support for this functionality.

Thanks