"Why a cold-air intake for an intercooled turbo?"
Because now the air entering the intercooler is even cooler than it would have been without it. Just think if it's 20F outside and ambient temps are going into the intake, it would have some cooling affect of the hot air the turbo is pushing into the intercooler.
I don't have proof of this but I was thinking the same as you before. Now, Im thinking differently so I bought the CAI WRX bonnet vent scoop from MRT to add to the intercooler I will be putting on.
BTW: I talked to a guy I know that drags his Supra on street nights at Atco and by him taking out his headlights at the dragstrip allowing cooler air in, he gained 2-3mph in his trap speed. Also, I posted that my trap speed went up by 1-2mph (96-97mph vs 94-95mph) a while back after adding the vent scoop to allow colder air in. And this is without an intercooler, yet.
[This message has been edited by Kevin Thomas (edited January 12, 2001).]