Is it possible with current featureset of Automated Build to add new tags from repository and tag the resulting image? Or do I need 3party service to automatically push new tags to Docker Registry?
Not at this time.
There is currently (Oct 2014) no Docker Hub API to create new builds or tags, so Docker Hub Automated Builds will only build the tags you've entered manually through the web UI. If you want to keep adding tags automatically, you need to docker push
your tagged images yourself.