Ran across this problem with my own Tommasini, although mine is an early 90's. I dont believe there is a cable tube inside the top tube. I replaced my old cables with some Campy Super Record cables and remember I had a bit of a time trying to fish the new ones out of the exit tube (near the seat lug). If I had to do it again I would pull the inner steel cable out of the housing (thats still in the bike) and maybe connect the old housing to the new housing someway, then pull it all the way thru.

After that just snake in the inner cable into the newly installed outer housing and your good to go. The inner cable will slide right on thru the new housing without any problems. As far as brake cables go, Campy Record has an inner teflon housing that slides inside the tougher outer housing. The steel cable slides inside it.

enjoy