WRT proxying, transparent proxies do what you discribed without you even knowing. They are generaly setup not to cache files over a certain size (about 4mb) and have a reletivly rapid rotation time or else storage would become insane (for obvious reasons)
SAIX, IS etc do mirror some of the majour shareware/software sites like Tucows, simtel etc.
There would probably be majour legal issues about mirroring microsoft.com or their patches. On top of that Microsoft would see little reason to bother mirroring their site localy due to a) Telkoms extortionate prices, b) The country is too small for there to be any point.
<hr noshade size="1">
Very funny Scotty. Now beam down my pants!!