In's and Out's of 'Abandon Bridge' ?

[LordDeadwood]

Also, just as an FYI, if the engineer unit that constructed the bridge is forced to retreat either through assault or by becoming broken, the bridge is gone as well. Ask me how I know that. Go on, ask me! 

And in that vein, I wonder why it is that you can't transfer maintenance of a bridge from one engineer unit to another? It seems like it would be a fairly simple and logical thing to do...