Stafford,
My understanding is that although they will work, Cisco does not explicitly support the SPA500 series phones on CUCM. If you use these phones with CUCM, they will be considered a 3rd party advanced SIP phone and consume 6 DLUs. The only exception may be the 502G. Because it only has one line, it may be considered a Basic SIP phone and only consule 3 DLUs. Would need to test this to be sure.
Hope this helps.
Brandon