With the release of CCA 3.2.2, the SPA 512 and 514s are now supported with the UC500. Please see announcement.
This is no longer valid:
Dear Cisco Partners,
The recently announced SPA512/SPA514 phones are not yet supported on the UC500 /UC300 platforms. Cisco engineering is in the process of evaluating it for support; however the dates have not been committed yet. We request you to kindly wait for Support for SPA 512/514 from Cisco before purchasing these phones. Thanks.
UC500/ CCA Team.