Hi Rob,
If it works then that's good, but just to be aware that there may be certain cases where our Plantronics device may behave differently depending on whether it knows there is a PC call in progress or not, particularly in the multi-line and/or multi-softphone user scenario, so I would tend to recommend you inform Plantronics SDK that it is on a call for both the incoming and outgoing call cases.
Let us know how it goes!
Thanks,
Lewis.