Ok, so in the ten mins since I woke up, I've been able to decompress the archives! Extracting them is quite a bit more difficult :/ I've found an extractor that can read the archives and spit out data about how many files are in it, but for one reason or another, it simply won't extract them D:<
Well, shitty :/ Basically, I've figured out that the extraction process is in two steps. First, we need to de-RNC the files (uncompressed). This is the easy part. Then we need to actually extract them. The problem is, the files themselves are split into tiny pieces in the .dat files, and the information on how to re-assemble them is in the .tab files. I found some tools that will do this for Syndicate Wars, but they don't work on TH because they also require a third, .pal file (which includes position information.) So in short, I don't think there are any more tools I can try :/
I'll have to look into the lua stuff.