Wow that's some old cable indeed! Yes it degrades or has long ago and by the sounds the lead in pipe work is stuffed or is not upto standard.
I recon you've laid out your options and it's a matter of picking one?
To make things cheaper there's no reason why you can't dig the trench to the boundary and employ the appropriate contractor to lay the new conduit. If it's going yo cost thousands this will certainly save a big chunk of that. Standard fee? You mean the $299? You'll still be paying that. I guess you have to weigh up the justification and on going costs of your current setup.