I am not sure of the specific technical name for the pipe, but here in Alaska the plastic "salmon colored" and other colored pipes are run for fire sprinkler systems in both commercial and residential now. Matter of fact, it's getting hard to see any new construction with anything but anymore.
Far as the flux, I believe it actually started after tests were done showing that, in improperly "flushed" systems prior to service, residues of fluxes such as No-Korode can come out in the potable water and, as such, possibly be even drank by end users, and this theoretically has been shown to cause everything from dental problems to actual poisoning.
Of course, everybody I know hates the stuff, and yes, on many jobs I've seen it used, by very competent plumbers who KNEW how to sweat copper, using high quality fittings and solder, leaks would occur shortly after. The stuff is great for washing off your hands but horrid for sweating pipe. And as I hate to admit it, alot of guys resort to the old trick of buying a tub of water-soluable, emptying it, and re-filling it with No-Korode to "trick" the inspectors.