Currently I am configuring Skype For PBX, I am quite to to the PBX scene, but this seems real easy to use. While there isn't a lot information regarding this service yet, here is a little info I can give so long.
On December 1, 2015 Microsoft officially added PSTN conferencing as a native feature for Skype for Business Online customers. For a number of years PSTN conferencing was offered through Audio Conferencing Provider integration in Office365 but this marks the first time that Microsoft has included this feature natively. There are significant differences in how the ACP provider integration works and how the Microsoft native provider works, so be sure to check out those differences to make sure your business and technical requirements are met. For most customers, however, the Microsoft Bridge (aka Microsoft PSTN Conferencing Provider) will provide the needed features and do it for a lesser cost than other services in the market. License Bundle Info
Option 1 – Purchase E5 licenses for your end users
The PSTN conferencing feature is included within the E5 suite purchase, so all you need to do is purchase the E5 suite, assign the E5 suite to your users and assign the PSTN Conferencing add-in license to your users. Users now have access to Skype for Business Online, PSTN Conferencing and any additional features available through the E5 suite.
Option 2 – Purchase PSTN Conferencing Add-In licenses for your E3 and E1 users
If you have existing E1 or E3 suite purchases, you would need to purchase only the PSTN Conferencing Add-in license for any users that will be hosting PSTN conferences. Users now have access to Skype for Business Online, PSTN Conferencing and any additional features available through the E3 or E1 suites.
Option 3 – Purchase PSTN Conferencing Add-In license for your Skype for Business Online Standalone Plan
This option will likely be less common, but if you have a Skype for Business Online Standalone Plan, you can purchase the PSTN Conferencing Add-In license for those users. An important distinction is that the Standalone Plan must be Plan 2; Plan 3 is not supported.
While the PSTN Conferencing Service is fairly robust, there are some limitations that may impact rollouts and usage of the service.