It's gonna be more difficult and time consuming than you realise. You can't export a whole map or anything of that size in the game without trouble. Things like .col's can only handle a certain amount of faces before the game crashes, so you'll have to split up the entire map into each building and each lane of road there is (either way you're gonna want to do it if you don't want the game to lag to hell), also depending on how big the building is, maybe splitting them into more than one piece as well (because of the higher amount of faces).
As well as that, you'll have to click, center, and export each and every piece of the map. Plus, with collisions, you'll probably have to remodel the entire map so each side of a building is one polygon instead of thousands of squares, otherwise you'll have to split the buildings up into even more pieces for the .col not to have too many faces as for it to crash the game. Even going so far as having to remodel some things like traffic lights and stuff, unless you want invisible walls everywhere.
Aaand as well as that, with the Map IO, you're gonna have to click each and every model (which will be thousands at some point) and assign it a number, for it to make an IDE/IPL. Which you'll have to have backed up the scene just after you split everything up, so the coordinates are right and ready for export.
Oh, and as well as having to do things for the sake of stability so the game doesn't lag to crap, you're gonna have to make LODs for everything as well, which is probably the most tedious task of them all.
Basically, chances are you're never going to get it done.