Here are a few questions that we need answered:
The interoperability testing within the DevConnect certification is usually initiated by the Partner as they are testing our IP phones to enhance their portfolio.
In the SSIP example for Avaya this was done by Avaya working with the Polycom Sales / Product management team.
Any feature codes would have to be implemented via SIP codes (star or hash codes) and could be replicated via Enhanced Feature Keys but again only Avaya will be able to answer this question.
Polycom Handset's, depending on the SIP / UCS version, can always utilize their available lines for separate server registration (only current exclusion is LYNC + SIP).
I would suggest you work with Avaya / Your Polycom reseller and a Polycom Sales Engineer.
Please ensure to provide some feedback if this reply has helped you so other users can profit from your experience.
Polycom Global Services