It is, it's just cumbersome to use. IIRC you press the right stick to get into the external camera, then hold down the right stick and press right on the D-pad and cycle through the cameras until you get to it. You can't shift zoom like you can with a keyboard though. It's honestly easier to just get a cheap wireless keyboard.
Since TSW2 you need to press and hold R3 and press the right arrow for exteral and the left arrow for internal cams. You can change stuff in settings that you directly enter: at the front window from the train, basic camera, or free cam