Why would they plan on replacing those piers? They look pretty good to me, and I'd expect that just putting a new roadway on the existing piers would be a lot easier than planting new ones in the bottom of the harbor...
That bridge is old, with over a century of salt water working on the piers from below and truck traffic vibrations working on them from above. I haven't seen any engineering reports so I'm not claiming to know. But if I went looking for such reports, I wouldn't expect anything before reading them, one way or the other. Maybe they're re-usable at a reasonable price compared to replacement, maybe not.