I found this MIB http://www.oidview.com/mibs/9/CISCO-DOCS-EXT-MIB.html
but for OID cdxCpeIpPrefixTable(1.3.6.1.4.1.9.9.116.1.3.10) i get ...
No Such Object available on this agent at this OID
So not sure if its just a configuration on the CMTS or i'm going down the wrong MIB
Cheers
:D
Deano