Clearly syndicated, to the point where last year the national True Oldies web site enabled streaming of stations in each time zone.
When this format started on 94.7 it ran for weeks until Chicago based programming started. Would have been funny if the ratings had risen early on, and if Scott Shannon showed up in the top 10 in multiple time slots. That would have been Chicago radio history!! And funny history at that, if a syndicated "non-Chicago" personality would have done well in 2 different dayparts.
Until Greg Brown and Fred Winston were brought in earlier this year for fill-in work, there were a few times when Shannon
went on live just for Chicago, although it was probably voice tracked that same day from NYC.