What is an alignment shoe on a steel bridge for?

You're speculation could be correct. it's hard to see what's going on from the photos. Could you post a framing plan and detail of the bearing?

Yeah, I just noticed those pictures were not very helpful in understanding the layout. I've attached a couple of pictures, along with the framing plan and bearing/shoe details. The alignment shoes appear to be specified only at the designated expansion bearings. I gather the bearings were a type of rocker bearing, but I don't see much allowance for movement or rotation. Perhaps there was an intent to allow longitudinal translation or rotation, but the bearings do not appear to accommodate any transverse movement.

Trying to upload better pictures.

Thanks for the drawings and photos. The "alignment shoe" is intended to keep the the expansion ends from moving laterally. Skewed bridges have a tendency to walk laterally due to rotation of the longer diagonal. The skews generally aren't that large ( there is disagreement about whether >20-degees but < 30-degrees is a problem) but the span on the right is a bit crazy. I give the original designer credit for thinking about lateral restraint before it became popular. I looked through some old MASSDPW design details from the 60's but no alignment shoe.