You don't need to use the zip-ties.
Your local bike shop should have cable guide adapters that take a hydraulic hose and will fit inside your cable stops.
I can't remember their proper name, but I always get mine from Leisure lakes bike shop, and they come in polished Silver, dull Silver or Black, and are made by I.D.
Another option used on mine...
...is to use a wire between the bosses with a sleeve that takes the Magura hose inside. Again, I got this from LL and it has been used since about 2000 (on another frame). If you look hard enough, it is just visible on the top tube. I think I used this method because I had a problem with the cable adapters on this particular frames' cable guides.
1990 Marin Team Titanium, 1991 Marin Team Titanium, 1993 Marin Team Titanium, 1994 Marin Titanium FRS, 1995 Marin Team Titanium, 1995 Marin Eldridge Grade, 1996 Marin Team Titanium, 1998 Marin DH FRS, 1999 Marin Team Titanium, 1999 Marin Mt. Vision Pro, 2000 Marin East Peak, 2002 Marin Mount Vision
1988 Concorde Colombo, 1997 Colnago Master Olympic, 2005 Look KG481-SL, 2009 Look 586
WANTED: Marin Titanium - pre 1990, 1996 FRS, 2007 25th anniversary