I'd like to use a single tag across different GTM containers. Did anyone manage to get a working solution?
Currently I duplicate the tag for each container.
If you have a constant setup, the most effective way is to use the export/import functionality in Google Tag Manager. Admin > Container > Import/Export Container.
In addition, Simo Ahava released a GTM tool allowing for Google Tag Manager containers to be cloned to other containers: check out http://www.gtmtools.com/.