right click and choose curve point, then select a curve point on the curve by mmd [middle mouse drag] then shift select the adjacent curve and rigth click on it and choose curve point [with the shift key still held down] mmd that curve point on the hsame exact spot as the other curve point.

-this will never be exact. even if u do it this way. tis just the nature of nurbs, they are mathematically calculated, but thisis as close as u can get doing it manually.
after the curves have been detatched, u can then point snap them on each other, positioning them right on top of each other.
-then u would have to tweak the cv closest to the snapped points to get the tengency to match properly.