I’ll add my own thoughts to this thread. I have quite a few cameras, and motion triggers from them would be very useful information. I do not see any reason for openhab to act as an NVR, there are too many other great alternatives out there, with so many features openhab could not hope to compete.
However, if OnVif alarms were supported, that would be a huge bonus. These is not much information or help available for OnVif that I could find. But, it looks like there is already a java OnVif library available and being maintained:
with a couple minor code examples here:
http://m.2cto.com/kf/201612/579714.html