You can simulate dual screen mode manually. Takes a bit of repeated “housekeeping”, but it works.
Rather than picking a resolution on the opening SETUP screen, instead pick WINDOWED (or just hit ALT-ENTER while the game is running). Now drag the window’s borders so it spans both screens. Then inside the window, drag the map to one screen. Whenever a pop-up comes up, drag it to the other screen. You can have all kinds of train “helicopter tracking” going on screen 2 and still see the map unblocked on screen 1.