I want to know if I can access the trace tag from within a rule definition via jinja interpolation.
Not really. Why do you want to do this?
I have a task in my workflow that is used to email admins if previous tasks within an orquesta workflow failed. In the email, it would really be handy to tell the admins what trace tag the current workflow is operating under.
This looks useful. Please open an issue at the st2 repo and request the feature.