Vertikal (471-481 King St E) | 23 & 19 fl | U/C

[panamaniac]

could that have something to do with shoring?

Hi panamaniac.  ZEBuilder is correct, it is for the shoring.  In previous photos you can see the tiebacks at each steel pile.  Also below is a snapshot of a drawing for this sort of thing.  It is a common method to support the shoring (and also in this project's case a method to puncture water mains lol).

It is unusual to see them box out each tieback like this, most often the concrete just covers up whatever steel is protruding from the shoring.  Perhaps it was too big and it interfered too much with the wall structure.  Regardless, those "portholes" will be patched in with concrete after the underground is complete and they can cut the tieback steel out of the way.

Thanks for the info!