Once again I've proven myself wrong. Apparently, you can have multiple techs with the same tech ID. Outpost 2 doesn't seem to mind. No errors or failure to load.
While it's interesting to know, I don't see any tangible benefits from this. It'll more than likely cause problems (as it did for me when I first realized this was possible). How? Let me tell you how I found out, it's easier than explaining:
I was working on multitek2 and accidentally assigned two techs the same ID. One tech allowed production of Robo-Surveyors and increased Common Ore Mine HP while the other increased Common Ore Smelter output. I researched the Smelter upgrade tech and was able to build Robo-Surveyors (but the Mine wasn't upgraded). Confused, I checked the techtree file and realized both techs had the same ID!
So if somebody can find a way to make this useful, congratulations. I'm looking forward to it.