Another author here - To answer your first question, no, this book is very front-end driven. We will have one server-side recipe that will use PHP. The rest of the recipes that use a backend use a "no setup required" server I wrote called QEDServer (http://qedserver.napcs.com/) which provides a JSON API full of records and a way to serve HTML pages so you can work with things like Knockout and Backbone without having to set up an API. We use it in a few recipes.

But we really wanted to keep the server-side stuff to a minimum, and while we all use Rails, it's not the answer to all web development - especially with things moving more client-side.

Your second question, yes you certainly can. I've done it and the only tricky part is making them work together, and thanks to web services, that's not terrible. I even have a new Rails app consuming some XML I wrote with classic ASP.