You best best is to work with a cabling contractor to lay the cabling. Let them worry about filling out all the permits and "right of way" stuff with the city. Large electrical contracting companies are good for this.
From there I can tell you what equipment you'll need.
How far apart are these buildings? Does the company own all the land? Will you have to cross any streets or public works spaces?
As far as cabling, your best bet is to run a ring of single mode fiber optic cable. The cable should be armored 24 strand and professionaly installed.