Sure. If you have Contact Center Express you could create a busy (instead of the more common cisco script) application and assign it a trigger. This would allow the call to route without errors from CUCM's perspective and the caller would hear reorder tone.
Without CCX I think you're stuck. You could create a DN, not associate it to a device and not set call forward conditions. This would result in a reorder tone should someone call it directly; however, the CTI redirect operation that Jabber invokes to divert a call would most likely fail. Essentially, the caller would likely not hear a busy signal, the Jabber user attempting to divert the call would get an error. You can try this to see what happens just to be sure though.
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