according to the manual, user.get method allows to :

• filter returned users by a specific media with mediaids
• filter returned users by used mediatype with mediatypeids
• return all user media with selectMedias
• return mediatypes used in user media with selectMediatypes

there does not seem to be a way to return only media entries that are assigned to a specific mediatypeid - for example, returning email addresses of all users, while ignoring scripts and all other types.