It depends on your definition of a "Disney" movie...
In the case of Life is Beautiful, Disney was only acting as the films U.S. distributor. Another company made the movie. Essentially, the studio is the booking agent that gets the film into the theaters in exchange for a cut of the revenue and/or video rights. Sometimes, the studio will invest some money in the film to buy the distribution rights up front. Anytime you see a company called Buena Vista-something, it is one of Disneys distributing arms.
Disney-produced films usually go under the Disney, Hollywood Pictures, or Touchstone Pictures production companies. In these cases, the company is the one actually making the film as was the case with Pearl Harbor (more or less). Even then, the production is really done by yet another company that turns around and purchases services from Disney and other companies.
Miramax is a wholly owned subsidiary that runs just like a mini-studio. It both produces its own films, funds others to make them, and buys completed films from other companies as well.