Absolutely, the pages (and that term is used lightly in the MVC side of things) can link between each other without any problems. Now, any built-in authentication or session management or anything like that will be considerably more challenging, but if all the sites need to do is link to each other then they can do this like any other two websites. The ASP pages can host manually-crafted (vs. HtmlHelper-crafted) links to the MVC actions, and can host forms that post values to the MVC actions (provided the field names line up properly).
There's nothing inherently special about the MVC actions. They're just handling HTTP GET/POST requests like anything else.