I also don't go into pushing out configurations from XML files on a TFTP server, but it may be the way to go if you're doing more than one phone.
New devices like the VVX500 and Spectra Link phones have only ever shipped with 4.x UCS releases, while older devices like Sound Point IP phones may still have previous 3.x SIP releases on them.
In order to utilize Lync integration a This process can be used on any of the Polycom SIP Phones which support 4.x software today (Sound Point IP, Sound Station IP, VVX, and Spectra Link models).
Also this process can be used to downgrade software if needed as multiple versions can be stored in the same location and a menu will be presented to allow the desired version to be installed.
All currently available versions of the Polycom UCS can be located in the official software release matrix online as well as on the product support page for any model SIP phone.
The Polycom SIP phones support a few different methods for software updates, most commonly utilizing a central FTP provisioning server so that all devices will check a single distribution point for configuration changes and new firmware images.