<p>I need your advice regarding migration. I want to migrate existing project to ASP.NET MVC and I can figure out the proccess except of url rewriting issue:</p>

<p>for example how can I make following route: </p>

<p><a href="http://www.eireads.com/ireland/mayo/cars-3/1263-used-cars-citroen-c5-for-sale.aspx" rel="nofollow noreferrer">http://www.eireads.com/ireland/mayo/cars-3/1263-used-cars-citroen-c5-for-sale.aspx</a></p>

<p>Or maybe I could somehow keep supporting legacy routes. </p>

I think you should really re-write your question and try to detail exactly what you are attempting to accomplish here.
If you are asking how to migrate an existing
WebForm
project into ASP.NET MVC keeping the same URL rewrite, the answer is; not easily. The models are too different.
Yet, you mention "routes" in the end, which make me think you are speaking like those of the System.Web.Routing namespace. So are you dealing with an existing MVC app and want it too look like that URL path? I can't tell. I am confused.