I recently was working on an environment with mixed OCS and Lync pools while they were migrating. One thing that came up was that despite having the new conference bridge number created for Lync the invites from Outlook were giving the old OCS bridge number.
I checked the conferencing number with the PowerShell command
This returned the correct pool and detail expected. I spent some time investigating before finding this way of forcing the number for the site.
Set-CsDialInConferencingAccessNumber -Identity "sip:firstname.lastname@example.org" -ScopeToSite
After running this with a minute the invites from Outlook showed the new number.