I think the importance goes up a lot if the rings are made of water as conjectured in parent. Getting access to water in space without dragging it out of a gravity well would make asteroid mining much easier. There's water in comets but their availability is not nearly as reliable.
Not really. At those distances, beyond the frost line [1] pretty much everything solid is bound to be mostly water. Ice is plentiful even in the main belt asteroids and in this case we're talking about the Centaurs that lie much farther away - of course, their distance also makes them ineligible for any short-term mining endeavors.
