VZW will not activate the BB Classic.  But if it is currently active on the network and is capable of utilizing the 4G network, it will continue to be operational on the network beyond 2019.  Phones that are utilizing only CDMA will no longer work after 2019.  These are the words of a VZW rep.  But then again, during this transition, you will get many different answers depending on which rep you speak with.

VoLTE capability is irrelevant.  VZW policy trumps.