Re: Mac
"and how much is because they're being given Skype for Business licenses as part of a Microsoft license bundle?"
Zero for the PABX side as far as I am aware - the only licences to use Lync Enterprise Voice are specifically for Lync. It doesn't come in bundles like ECAL for instance - you only get Lync Standard or Lync Enterprise - not the Voice license.
Biting the hand that feeds IT
