This doesn't directly answer your question, but instead of Knology VM, you could set up the OBi to send unanswered calls to a different (free or paid) VM system that does correctly show MWI and VMWI on the OBi.
The new VM may also offer other advantages, e.g. notification by SMS or email, a nice web interface, etc. or may be less expensive. What features do you currently have on your Knology line?
