The Summit Stage is alive and well. While I don't ride it very often, I'm pretty sure it makes stops at many of the Summit ski areas. Here's their website so you can see where it stops. http://www.summitstage.com/
the kab bus(keystone-abasin-breck) no longer runs. you can still catch a daily shuttle to vail from either keystone or breck or both, check their sites.
the summit stage(searchable online) is your only bus option to get around breck to keystone and its on a bus route. expect at least 45 min. one way.