We manage a number of reverse DNS domains corresponding to most of the CUDN IP address ranges. Most reverse DNS in Cambridge is generated from the IP Register database except where control is delegated to institutions. Rather than listing all the details here, you can consult the sample configuration for stealth secondary nameservers.
In Cambridge we have a relatively unusual setup for parts of our IPv4 reverse DNS: we use DNAME records to reduce the number of zones that we need.
The historical notes describe how the scheme has grown over the years.
There are some notes specifically about reverse DNS for 10.0.0.0/9 explaining how the
10.in-addr.arpazone is shared between institution-private and CUDN-private addresses.There are some more technical notes on consolidated reverse DNS which are less Cambridge-specific.
There is a draft revision to RFC 2317 which includes this DNAME scheme; however the draft was allowed to expire without passing through the IETF standardization process.