Certificates are important in the Lync infrastructure. They are used to authenticate, sign, and secure communications. It is important to have a strategy on how to restore the Lync functionality where certificates are highly indispensable.
In the Don't forget the infrastructure – the greater recovery plan section, the internal PKI is listed. There is no point in backing up or restoring certificates issued from the internal CA, unless this is on the disaster recovery plan for the company. This section is worth reading if the PKI is on the restore list or if Lync is the only service we have to restore.