The old seven mile bridge was built by Henry Flagler for his railroad. I think that you will agree, that at some point, it was converted from a railroad bridge to a automobile bridge. The main problem was, that is was extremely narrow and there were lots of deadly car accidents on it. So they got the new seven mile bridge.
I don't know about Peach, but the "fake train" I mentioned in my earlier post is in this picture in the foreground.
Here is a pic of the entrance to the old seven mile bridge.....notice the "No fishing from Bridge" sign.
Here is a pic from farther down the old seven mile bridge. Notice the fishing pole on the right. Also notice the Speed Limit sign. In the far distance you can see the trees on Pigeon Key. I can't really see the teams having to walk or run all that way. If you look at the roadway on the bridge, they have taken those concrete stop bars used in most parking lots and used it to divide off the driving lane down the center and the walking paths on the outer sides of the bridge. At some point, they do have to have maintanance vehicles go to Pigeon Key for electical, plumbing, etc. I would suspect that since WRP rented the island, they would be able to use that method to get all their equipement down on Pigeon Key to film the Finish Line.