UC500.com Cisco CallManager Express, UC500 reference

Cisco Systems is pleased to announce the availability of two new products to enable enhanced call coverage for power users: Cisco Unified IP Phone Expansion Module 7915 and 7916. Call coverage is a critical capability for executive administrators and others who monitor and manage the various status of calls. For high call volume positions, the Cisco Unified IP Phone Expansion Module 7915 and the Cisco Unified IP Phone Expansion Module 7916 deliver an adjunct solution to instantly determine the status of a number of lines beyond the number supported natively in the wideband audio Cisco Unified IP Phones 7962G, 7965G and Phone 7975G. The Cisco Unified IP Phone Expansion Modules extend the call coverage capabilities with additional buttons and an LCD display.
Key Features of Cisco Unified IP Phone Expansion Module 7915 and 7916
The large, high-resolution LCD display allows for quick and easy identification of associated buttons. The Cisco Unified IP Phone Expansion Module 7915 has a grayscale display; the Cisco Unified IP Phone Expansion Module 7916 has a color display.
The Cisco Unified IP Phone Expansion Module 7915 and 7916 feature 12 physical keys with access to 12 additional keys via the page keys. This adds a total of 24 buttons to the existing six buttons of the Cisco Unified IP Phones 7962G and 7965G and the existing eight buttons of the Cisco Unified IP Phone 7975G.
Up to two Cisco Unified IP Phone Expansion Modules 7915 or 7916 can be used with Cisco Unified IP Phones 7962G, 7965G, or 7975G.
Users can adjust the contrast or brightness of the individual LCDs for the Cisco Unified IP Phones 7962G, 7965G, and 7975G and Cisco Unified IP Phone Expansion Module 7915 and 7916 according to their preference.
The buttons on each Cisco Unified IP Phone Expansion Module can be programmed as a directory number (DN), line key, or speed-dial key, much like the Cisco Unified IP Phones 7962G, 7965G, and 7975G. When used as a DN key, buttons are illuminated, allowing easy identification of call state.

Cisco develops Communication Manager Express for the ISR platform first. It will make its way to the UC520 eventually.
From what I have heard from folks at Cisco is that CME releases generally take a couple of months to be ported to the UC520 platform.