Sitefinity is built on top of ASP.NET WebForms, not ASP.NET MVC. This means that the project will not be able to work with ASP.NET MVC user controls. However if you rework your user control to work on a ASP.NET WebForms application it will also work in Sitefinity.
the Telerik team
Do you want to have your say in the Sitefinity development roadmap? Do you want to know when a feature you requested is added or when a bug fixed? Explore the Telerik Public Issue Tracking
system and vote to affect the priority of the items