hi,
if it is a windows server you might want to look into wmi events and how to execute scripts if the events get triggered.
basically you want an event that triggers on adding a new file to a specific folder, the script that gets executed should then call the CA-RA REST API to trigger a deployment.
I have no knowledge though regarding the wmi events, I was first thinking about writing a windows service which checks everything, but wmi events might be something useful as well. was just something I grabbed from a quick google search.
what you also could do, but I wouldn't recommend it: set up an infinite "deployment" in CA-RA that polls for new files in specified servers and if it finds a new one, you then again use the REST API to create a new deployment based on that file or whatever you need.
best regards
michael