This problem certainly won't go away unless you can 100% prevent the initial water entry from the utility end. I can vividly remember my cousin filling junction boxes in underground mains with molten pitch in the late forties, [because I got a whack round the ear'ole for throwing a stone in the pot!]. I'd guess a modern equivalent would be a compound-filled gland - maybe like this?
http://www.douglaselectrical.com/?gclid=CLax-fSwxZ4CFVBd4wodfDDUog As to the water already in the wire- most of that's probably in there for good. Question is, how long will it take before it all fails due to corrosion?
