Funny thing is if you ring an extension that has one busy call appearance, it call waits on the second call appearance.
If you program a user button, it will be underlined (busy)
If you press this button it will give you options to call wait, callback etc.
If only on the IPO.... when you ring an internal extension, with call appearances, when one was busy it gave you the same options (like every other system)
Hope this becauses a feature request... It's only been 3 years now