Tom Anderson wrote:

This is not an authoritative answer, but i did finally notice that
according to Quail, they do cross, and the crossing is indeed a little way
south of Harringay Green Lanes; probably too far to build a station with
interchange, though.

On a more general note, how can one go about getting accurate information
about the routes of underground railways? Are there some sort of official
maps somewhere?

Referring to the fold out maps in the now discontinued TfL "Out & About
Guides", the lines cross somewhere in the vicinity of Eade Road & Vale
Road, just north of the Woodbury Down Estate.

--
Phil Richards
London, UK
Home page: http://www.philrichards1.pwp.blueyonder.co.uk