I am also a proponent of underground utilities whenever it is reasonably feasable to do so, but in this case it would have not prevented the problem. Mainly because there is no way the cable owners are going to pay for underwater excavation - they could not "pass on" that kind of expense very easily and so ... they would still have to route cables over the bridges, etc. and hence still having to deal with similar problems. Might be a better idea to "harden" the above ground links as it would be much cheaper to do so.