There is only one other application that I know about that uses Proxy ARP with subnetting, also here at the Australian National University. It is the one that Andrew Tridgell originally wrote the subnetting extensions to Proxy ARP for. However, Andrew reliably informs me that there are, in fact, several other sites around the world using it as well (I don't have any details).
The other A.N.U. application involves a teaching lab set up to teach students how to configure machines to use TCP/IP, including setting up the gateway. The network used is a Class C network, and Andrew needed to "subnet" it for security, traffic control and the educational reason mentioned above. He did this using Proxy ARP, and then decided that a single entry in the ARP cache for the whole subnet would be faster and cleaner than one for each host on the subnet. Voila...Proxy ARP with subnetting!