Hi Jan!
Workspace is started when workflow is called in batch mode. This can be seen if you delete your workspace (Do not try this at home if you do not have a backup!) and then call a workflow from command line as it will create a workspace 
Not sure. I carried out my project using call-workflow approach with batch mode. Development is harder and troubleshooting is a challenge but workflow are still running every day. At least I do hope so 
Additionally take a look at this topic:
Br,
Ivan