Hi Steve –
In general, the recommended source for this kind of content is the InfoChannel Mitel Solutions Alliance (IC MSA) portal, not the KB. There’s a current certification for the Mitel TA7108 with MiVB 9.1 published on IC MSA, and per the “Software & Hardware Setup” table in the published Configuration Guide (CG# HO974 V2), this certification is also valid for all the Mediatrix devices that share firmware with the TA7108 (including the C-series). If you don’t have access to the IC MSA portal, your Mitel reseller can download and provide you with the CG. All that said, Mitel does not certify the Mediatrix devices for FXO operation. For FXO with MiVB, we recommend that you use the AudioCodes (CG# HO1844 V2) or Adtran (CG# HO2037).
Hope this helps.
Dave Lowenstein