The guy doesn't visit the forum, and I don't see him much in the last year or so. I'll see if I can get hold of him and ask him if he has any particulars.
BTW - this is not only known by the rich here. The poor (at least some) know about it, but don't often bother themselves to do much about it. For example, my wife's sister bought some property in Jose C Paz. It is in an area where a few poor folk got together and took over some abandoned land, then started parceling out plats to other poor folk. The guys who set it up originally (I don't know them) talked to the local municipality to make sure it was abandoned and even asked what they needed to do to make it legal. Of course, they never did anything, but everyone who bought plats from these guys, the guys told them where they needed to go to make their plats legal, with title and all. As far as I know, no one bothered to actually go through the process of proving improvements, paying the taxes, and so on. They do, however, dig down to make septic systems and when they encounter the municipality's sewer system they tie into that without charge, as well as electricity. Heh.
This is a good reason the family of the person you know needs to be careful - in the provinces (well, even here in the city it happens as well), if land is not occupied, it often gets occupied illegally by squatters, whether or not the taxes are being paid. And we all know what happens when squatters get involved here...