As a random aside, Day of the Condor is Kevin Mitnick’s favorite movie. Mitnick was probably the most famous hacker in the world at the time Sneakers was being cast.
That's really cool. Turner's phone company background was a very interesting facet of his characterization. I'm sure it was to many a Sneakers-like experience.
Personally I liked this factor, and the Higgins character, enough that I outlined some fanfic in which Higgins quits the agency and convinces Turner to help him out on various freelance jobs. I thought they made a very rationally-sympathetic pair in the film.