Visibility rules?

[GottaLove88s]

Pip/Iain, What are the rules that make enemy units visible? I just accidentally double clicked a tree while my tank was selected (apparently a rapid double click fires if a unit is selected... argh!!...Pls can we have an option to disable double click to fire?). I've noticed that if opponents fire at random trees, hedges or fortifications, etc, the BA iPad version displays the enemy unit's location and the action it's performing... even if I have no units (or air cover) anywhere nearby that would realistically be able to see that animation... Dangerously helpful intell (except when I double click on trees darn it)... PS. this isn't true for artillery which stays genuinely hidden during a bombard action. I wonder if artillery shows to the enemy during a regular shot (rather than a bombard)?