There isn't really a mapping between backbones models and protorpc. Backbone.js assumes the model layer is RESTful where protorpc assumes you will make method calls, each via a POST call.
I'm interested in what a model layer would look like using protorpc. One idea is to take a similar path of abstraction as the underlying appengine datastore api does: use protocol buffers to express an "entity". So you might have:
This would be a proto definition called, "Entity". From here you could build procedure calls that send entities for doing common routines, such as updates, or deletes. If you can make a structure like this work, you can build an api with javascript which hides the protobufs from you all together.. When you call Model.get('Book').create({title: 'My book'}), it constructs the Entity protobuf and calls the remote call for creating a new entity.
I don't see it mentioned very often, but google's closure-library has some really phenomenal patterns for building maintainable javascript. Its worth checking out Michael Bolin's book, Closure: The Definitive Guide, which goes in depth of the Component and Control frameworks.
I've been using the library for 2 or 3 years now, and I am always surprised to see it has such a small community.
I don't think the intent is to really be a reference for javascript methods, at least for now. Apple releases "Coding Guidelines" as more of a style guide and suggested patterns.
From the toolkits:
"JavaScript toolkits enhance productivity but often carry a significant memory footprint that may slow down your JavaScript application. When using a toolkit, try to reduce the toolkit’s footprint to just the APIs that you use in your application."
This somewhat hints to me that Apple will come out with a framework that allows more modular includes or compiles similar to closures system. This is somewhat a hit to jQuery's "all-in-one" setup.