Mine has had this conversion done to it. On mine it looks like the rubber hose runs from the caliper the toward the front of the car where it mates to what looks like it is the original metal brake line. It is right where the metal line goes under the sub frame and goes through a metal tab on the frame (looks to be a stock tab). There is a threaded fitting there that the rubber line is connected to (This again looks stock).
Just looked again, it's almost certainly a stock fitting, either that or the guy that did it did a kick ass job and spent way to much time making it look stock. If you look in the gap between the leading edge of the tire and the fender well clear at the bottom near the rocker panel, you should be able to see it on the sub-frame rail, just above the swing arm thing for the rear axle. If I get time later and you still cant find it I'll take a picture.