Are there any labs available in the sandbox which include an instance of Unified Communications Manager Express (CME)?
Not currently. Can you provide a little bit of information on the CME API's you would like to work with, and the use-cases that would need to be supported?
I'd like to verify that our third-party SIP-based hardware endpoints (broadcast audio devices) are able to register, make and receive calls. It would be a pretty simple use case - configure a few users (with digest auth) for the hardware devices and softphones for testing, configure directory numbers for them and confirm basic calls work between them (G.722 and G.711, unencrypted SIP(UDP)+RTP). So I guess it would be voice register pool, voice register dn and a bit of global configuration. I've been running similar tests against the various CUCM releases in the lab via an Easy VPN connection from a router here, which has worked very well; ideally I'd like to replicate those tests on a CME device.
While you can likely get an RFC standard 3rd party SIP device to connect with CME and place basic calls, note that Cisco does not officially support such a configuration for customers :/
Retrieving data ...