I have come up with a solution that allows proxies notifying each other. I posted an example on
http://blog.pietergrobler.com/node/3. Basically, proxies subscribe to another via a service. It would be interesting to get feedback on whether this is good practice or not.
I will also be posting more on proxies whose service can be reserved. This enables large data sets to be sent to garbage collection when the proxy has no active reservation.