Integrate Yii framework with another Framework

Hello, the question its, can i integrate another framework inside yii and then integrate another yii app inside an existing app?

Let me explain…

The background:

We start our website in atomic framework (why? i don’t know, the developer leader decided to use it) and all our front end web page it’s in atomic framework, then we have to develop the back end and they say “why no’t to try Yii?”

so… we develop in Yii our back end (Charts, reports, statistics etc…). The we talk about our next deployment, a new module for our front end, and because we find easy to deploy in yii we decided to use Yii.

We develop in yii the new module for the web, this module never contact the original web in atomic, its an stand alone module with a sheared DB and Search engine.

The 2 Yii apps are using common files like Models and Configurations, but …

The problem:

Now we have 2 different Yii apps the back end and the new front end module. And we have our core front end in atomic.

The hole system its working fine but we have a problem. The maintenance!, that little bastard!!

And now, we need a third Module that uses an yii app and the atomic app.

If we need a module inside the atomic app we need to rewrite all of it because it is not inside my yii app!

then again after the develop and deploy we have to …yes … do the maintenance!!

The Question:

Can we integrate the atomic app to Yii in a “easy mode” that doesn’t take much time?, we are talking about that in 2 weeks we start the develop of our 3 Module of the website.