Check out the English examples here: http://en.wikipedia.org/wiki/Non-English_usage_of_quotation_marks#Quotation_dash
In, for example, "Dubliners" Joyce puts the speaker tag at the end a lot. He appears to just be doing away with conventions of a lot of punctuation that isnt necessary. In something like "Trainspotting," it appears to be more of a dialectical thing, where he doesntisn`t necessary. In something like "Trainspotting," it appears to be more of a dialectical thing, where he doesn't use many speaker tags at all. Other writers use both to distinguish 2 types of speech.
I think that there arent really any set rules, as most writers who uses dashes use them for the fact that it is different or does something that puntuation marks dontaren't really any set rules, as most writers who uses dashes use them for the fact that it is different or does something that puntuation marks don't. But you might run into trouble with editors.
