I wish there was a msRTCSIP-GroupingID function for the dial-in conferencing numbers. Same way as it is possible to group users together in the address book with grouping id, it should be possible to block/allow access to dial-in conferencing numbers.
This relates to the Lync On-Premise version. In one environment I work with there is 35 dial-in conferencing numbers, in different countries. It is fine that they are all listed on the https://dialin.company.com page. Access to the page is anonymous, and hard to filter out something from that. Anyway they should only be able to use the conferencing number added to their region. Problem is that users are able to choose a region number that they do not belong to. The voice channels from the SIP provider belongs to the users in their region, and should not be potentially filled up by other users in the system.
Region can be set through Lync control panel or New-CsDialInConferencingAccessNumber. The way it works now is that as long as a user has enterprise voice connected to a dial plan, which is member of at least one region, the user can choose from every conferencing number in the Lync system.