what does this ! mean when next to abridge on the map?

[Green]

Also while playing Minsk 44 last night my units advanced into the south hex of a ! bridge and a box opened saying 'bridge has not been demolished'.
So I assume now that ! stand for damaged or wired for demolition bridge. That may or may not be destroyed by enemy forces using it.

No, there is no on-map display of a Wired bridge. This status is only displayed in the hex info box (using right-click). Perhaps the hex you were looking at has more than one bridge?