Almost all of the live action is film yeah. Unless there are effects composited onto the film.
The models seemed to have been filmed with video, hence why the DVDs are a nasty mixture of telecined film (live action) and 30fps video (models). Although there are some model shots in the first few seasons that seem to have been shot on film because they are telecined.... Maybe the ILM stuff.
It must have been much easier and quicker to do the model shots and such on video. Obviously these guys were under insane time pressure and the show got progressively more space action.
It'll be a bit of a shame to lose the model shots in a HD release but the models were not built to withstand that kind of image quality. They have a lot of flaws that don't show up too much in 480p. But we'll start seeming crooked stickers and stuff if we can examine them in 1080p.
Especially with that 4 ft model and its over-the-top hull detail.