You can't switch back and forth between panniers and the baskets. The baskets bolt onto your rack frame (which is why they are so rarely stolen). There are some metal tabs that you will bend to fit. Once you get them on, those puppies are staying on.
Now, if you have a second bike that you want to set up as a hauler, the baskets could just stay on that bike.
Or you could do like Geonz suggested, and set it up with an Xtracycle and make it a dedicated super-hauler. http://www.xtracycle.com/cargo-bicyc...o-bicycle.html

