When you say, "engaged tone" what exactly is that?
A busy signal?
Ring with beep? (Call waiting tone.)
Busy is easy, the busy command plays that. Ringing is also easy. Call waiting tone isn't one of the options available.
There are not too many standard signals that can be played to a caller, but you could probably record any tone that you wanted and attach a music on hold player to play the tone that you want callers to hear.
Simply queue the call, and then use a 'wait' command choosing the announcement as the source the caller would hear.
I don't think I'd use standard announcement boards for that. The tones could confuse the board, and the last thing you want is corrupt announcements.
Carpe dialem! (Seize the line!)