To update lync phone firmware from lync powershell.
1. Extract downloaded file from Polycom and not the location of the cab files
2. Open Lync Powershell in Admin mode and run the following command
Import-CsDeviceUpdate -Identity service:webserver:<LyncFEseverFQDN> -filename (where filename is exact path to file)
Example : Import-CsDeviceUpdate -Identity service:webserver:lync2013fe.domain.local -c:\temp\UCUpdates.cab