txgman - it kind of sounds like you are expecting a high volume of calls on private lines. Yes, you can call forward/busy the private line to the main number, but that is done at the telco level.
Think about this. The DK40i, with the proper software level and motherboard version, will support a T-1 or PRI. Some CLEC's will provide a fractional T-1 with as few as 8 channels. If you can do that, then program DNIS digits to your phone and you should never get a busy!
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