I wouldn't reccomend an electronic fence to even the most well behaved dog let alone a dog with aggression issues. I don't know if you saw it or not but just this morning on my way to work I rescued a dog that had gooten out of his fence & was too scared to cross back into his yard.
See the thread here: http://petoftheday.com/talk/showthread.php?t=92680

There are many other reasons why electronic fences are not good. I'm sure if you do a search here you'll find a few good posts about the negatives of electronic fences.