In order for that to function as it did originally, you'd most likely be looking at a full machine rebuild. That includes re scraping the ways and table, as well as replacing every bearing in it for starters. This is not a cheap service. My guess would be $7-10,000, as it is a very labor intensive process.
As someone who enjoys quality equipment and bringing old pieces back to life, I can say with a good deal of confidence that your looking at scrap value. Sad to see a nice mill neglected like that.
Another thing to keep in mind is that the machine you looked at is in a larger class than a typical series 1 Bridgeport that is so commonly found. We're talking 5 HP, increased X,Y,Z feeds, and 4,000 lbs of iron. This is great if you need it, but it can be a bit of a burden if your short on floor space.