WB stations to join CW, UPN stations to NOT join CW:
New York, Los Angeles, Chicago, Boston, Dallas, Washington, D.C., Houston, Miami, Denver, St. Louis, Portland (Ore.), Indianapolis, San Diego, Hartford, New Orleans and Albany.
I'm pretty sure this has something to do with WGN, which, at least in Chicago, carries WB programming. All of these other cities also get Tribune-affiliated stations.