Excellent information; thank you all.
And Tesla, I'm thinking along the same lines; it'd be great to use the existing raceway, if possible. There's a lot of sidwalk, driveway, lawn, and plantings to tear up if they run new conduit.
On the other hand, I'd expect that the original lead-sheathed conductors were pulled in with soap as a lubricant, and could be pretty well stuck.
Thanks again,
Cliff