Like the Galactica pilot, it was shot as a TV pilot, but was released theatrically as a movie before the series premiered.
I could swear I remember the Galactica
pilot only being released theatrically after
the show was already on the air, at least in the US. Are you sure?
Yes, the BSG was released theatrically in the U.S. AFTER the series had its run on ABC (it was done prior to the premiere of the 'Galactica 1980' TV series.) It might have been released in Canada and in the European markets prior to BSG's premiere as a TV series in the states. (I always liked that in the theatrical version, Baltar gets his head chopped off by the Cylons after the Colonial Battlestar fleet is destroyed.)
The Buck Roger's in the 25th century film was released to theatres prior to it airing as the series pilot in NBC.
I did see the Buck Rogers prior in the movie theatre, and to my recollection, it was not shown in widescreen format.