Even though they've done away with the branding years ago, it appears that they still have an active trademark:
http://tess2.uspto.gov/bin/showfield?f=doc&state=4008:pq1e1q.2.14
Conversely, the trademarks for "WGN Superstation" and "Superstation WGN" (the channel is now known as "WGN America") are listed with a status of "dead".
http://tess2.uspto.gov/bin/showfield?f=doc&state=4008:pq1e1q.2.14
Conversely, the trademarks for "WGN Superstation" and "Superstation WGN" (the channel is now known as "WGN America") are listed with a status of "dead".