Northern line for openBVE (1998 era) is here.
1995 Stock for openBVE is also available on the link above.
Northern line v4 for BVE4 is currently unavailable - coming soon!
Northern line v3.1 for BVE2 is here
Northern line v2 for BVE2 is below
Northbound route here
Southbound route here - Note the 2nd link works properly with winrar if you want the route file without the error.