Well.... cars don't honk at one another when they pass.....
I don't know the area in question, so I don't know the particular situation, but as it is a road and not a MUP, I'm more inclined to agree with aicabsolut. I don't call out to cyclists when I am passing them on the road, just as I don't want to be honked at by cars. Then again I don't buzz them either. I give them the 3 feet or more that should be given by a car.
While some states may have an "audible signal" law, others have a prohibition.... its actually illegal to honk at cyclists for no good reason (ie an actual dangerous situation that requires use of a horn) in this state. I prefer it that way. For the most part I can hear cars unless it is very, very noisy. I know full well they are there. When they let out an ear piercing honk right off my side, it just makes me jump and that's not good.