Considering the quality of pro digital images these days, I've been expecting the Audubon Engagement calendars to start to include them, but this has not been the case.
They include images using large format, medium format, and some 35mm, all film. I appreciate the fact that they do list the gear used, and the exposure.
Do you know the selection process for the images? I see that some are from stock houses, like Larry Ulrich. Stock houses have been slow to adopt digital, so perhaps that's the main reason.
One thing with digital is that people can go overboard with Photoshop to the point where the image becomes an oversaturated digital painting instead of a photo. It's harder to cheat with film!