Going to post a response to my own query here, in case this helps anyone else.
Have not found a mechanism of querying the status of synthentic jobs via REST API, but what we have been able to do is:
Define a Policy for the job(s)
Use the "Alerts and Respond API" (https://docs.appdynamics.com/display/PRO45/Alert+and+Respond+API) to query for Events using an event-type of POLICY_OPEN_CRITICAL,POLICY_CLOSE_CRITICAL
One downside is a Policy must have an Action associated with it. Our controller is SaaS, so our options to use custom actions is limited, we ended up defining a Email action and post the email to a "Black-hole" mailbox.
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