(This article is currently under construction!)
1 Overview
Microsoft Urban Assault supports the completely free mouse cursor movement during the gameplay. This essential function is primarily used to interact with command interface or perform various actions directly on the 3D world screen, which is a crucial feature for implementing the RTS-style gameplay and functionality appropriately.
By default, vehicle controls in the FPS-mode are usually accomplished via either a keyboard or a joystick (as recommended by the developers). But the player can always decide to activate/deactivate the 'Mouse Control Mode' at any time by clicking the right-mouse button while occupying a vehicle in order to control units with both mouse and keyboard, or mouse and joystick inputs simultaneously in the first-person control mode.
2 Mechanics
The Mouse Control Mode function allows for more precise and reactive FPS controls in vehicles for the player, but sacrifices some (or most) control over the RTS elements as well since the mouse cursor movements become locked to the first-person view and reticle of the vehicle. Therefore, the player should make a prudent decision when they should activate/deactivate the mouse control mode based on the situations and tactical/strategic needs (if they intend to use it).
The simultaneous input that becomes possible with the mouse control mode also has an additional benefit, where the players can manoeuvre their vehicles faster than usual in the first-person mode by applying both Mouse+Keyboard or Mouse+Joystick inputs together simultaneously. Apparently, this is not a bug considering there is a game document referencing this feature.