In the radio interview referenced above somewhere (which may or may not still be available online), Hansard talks about meeting Dylan in Dublin, in some kind of backstage/post-gig context. I'm fairly sure (although not absolutely positive) that the meeting took place before the filming and release of Once ~ at least, that was my impression and assumption ~ which would mean that Bob had already been aware of Glen and his music and the Frames before seeing the film.

In any event, Glenn relates that he was a bit tongue-tied and didn't know just what to say, but managed to blurt out that for him, the meeting was something like what meeting Woody Guthrie must have been for Dylan, and then the ice was broken and the two were able to converse a bit about Woody and then go on to related subjects...