Is it possible to integrate MIP SDK with APU FD322 from Fibersensys?

Yes.

Looking at https://fibersensys.com/product/fd322-rapid-fiber

I notice - “XML via Ethernet and form C dry relay contacts..”

The way i interpret this you would be able to use normal device inputs to put this on an XProtect. Perhaps more interesting or flexible, you could develop a service that receives this XML and submit it to XProtect as Analytics Events.

On Analytics Events I recommend this read: http://download.milestonesys.com/MIPSDK/Samples/TriggerAlarmFromExternal-ConceptSolution.pdf

Looking at the Fibersensys web page I thought it was all very familiar but then it dawned on me; the Milestone Custom Development has made an integration but with what must be a competing product to this Fibersensys product. https://www.milestonesys.com/solution-finder/milestone_systems/southwest_microwave_intrepi_series_II/