On-network conferencing for Microsoft Teams is simply the ability to make calls to Audio Conferencing Service numbers across an organisation’s Direct Routing deployment. For example, this might be handy during a migration project if you want PBX end users to be able to dial into Teams Meeting from existing 3rd party IP, Digital or Analogue handsets.
As shown in the video below the On-net conferencing feature supports both dial-in and dial-out from Teams Meetings. The dial-out function is enabled by creating an Audio Conferencing routing Policy (New-CsOnlineAudioConferencingRoutingPolicy) and assigning it to end users. For more information please refer to the documentation.
Note: At the time of writing this capability is currently in Public Preview.