MVC is a design pattern that can be implemented in many languages including PHP, ASP, NodeJs, etc:
http://en.wikipedia.org/wiki/Model%E2%80%93view%E2%80%93controller
If they have PHP enabled, then by default they have MVC enabled (well it is not something enabled but created). You shouldn't have the need to install new extensions to have MVC. It uses pure PHP (and whatever backend you choose: mysql, mssql, etc..)
You have the option of creating a new MVC structure (Framework) or using existing ones, some of the top of my head:
- Zend
- Codeigniter
A tutorial I found on Google for making your own MVC: