As far as I know, they are all on a spot beam, with the exception of WGN.
WGN's local programing bears little resemblance to the national WGN's programming.
According to our local TV guide in the newspaper, which has both listings, today, from 4PM CDT until 12 midnight, the only time the programing is the same for both, is for the 9 PM News and Sex and the City at 10.
But according to this http://www.tivofan.com/directv/channels.html#884 Channel 66 , WGBU, is on a national beam.