It could also be equipment related to the electric switch lock.
Monday night (12/7/15), there was a temporary 30 mph speed restriction from CP 4 (QB 4.85) to QB 4.26 (Franklin St / Regina Pizzeria). I didn't hear if that temp speed restriction has been lifted as of this AM.
There is a new 3 light signal tower for CP 4 track 2 eastbound. Not sure why they went from 2 light to 3 light signal? The old 2 light signal tower has been removed. And I don't think they changed the tower for track 1 eastbound - I think it is still 2 lights. The westbound single track CP 4 signal is the 2 light dwarf signal that was previously / originally the signal for the connection from the freight / yard lead into CP 4.
The temporary stop boards on either side of the work zone (eastbound at QB 5.09, Market Street overpass, westbound at QB 4.26) are still in place as of this AM. Track foreman gives permission past them without any trains actually having to stop at them, so they haven't resulted in delays (except for the first day they existed, when they created all sorts of havoc).