The railroad already packages with the mine through Mild to Wild tours. You can take the train up and a bus will drive you up to the mine and back to Silverton for lunch and then take you the rest of the way back to Durango. The ticket sales help support the mine, another tour company, and the D&S. From the customer's perspective, it is a seamless and well thought through package that allows them to see more than they usually would in one day and still make it back to their hotel in Durango for dinner. This is just one of the many packages the D&S offers passengers, everything from Raft and Rail, ATV tours, horseback riding... you name it. They work with probably five or six different providers already.
Getting off of one train, boarding another, and taking an hour or so to get to the mine is not something the average family market will do. A specific group of people would... and while they would contribute to the overall economy by most likely spending additional time in Silverton, I doubt that it would be as drastic as some people think it would be. From a railfan perspective it would be really, really, really neat. From a business perspective... the D&S has worked hard over the years refining their current packaging promotions and are very successful with them.
Al not supporting the Silverton Northern project doesn't mean he doesn't care about history, he just understands how the tourism industry works.