yes, the KM grid system can give pretty accurate locations. Combined with target courses, speeds, sea states and winds, and reports updated every hour (if shadowed by a contact holder U-Boat).
Like we know, the game gives us only approximate location, like "DE 86". So it doesen't represent minor quadrants at all. Should be like "DE 86 52". Every Grid (DE in this example) were divided usually in 81 major quadrants (there were exeptions) which were then divided into 81 minor quadrants. There is a good site about this, but I don't remember it anymore
Krupp