Vaadin alongside old JSF 1.1 / spring web app?

I need to extend a pretty old web app based on JSF 1.1 and spring/hibernate. Basically adding some model objects and crud and bulk editing functionality.
I have no experience with Vaadin yet but it looks like a great framework for the type of data management I need to do.

Do you think it is feasible to integrate Vaadin with the old app? They would have to share authentication and access to the database.

Looking forward to your comments!