I understand they:
1) are upgrading to 45mph switches (30mph with current signalling)
2) improving the location of the switches in some cases to reduce congestion points
3) improving storage area to store 12 car trains and possibly more trains than before
It is bound to improve things a little bit.
Yes the 45mph switches have been installed in the east end of the corridor between miles 1.4 & 1.7 of the Eastern USRC limits (mile 0.0 being the center of Union staion) replacing the old 15mph turnouts at Cherry st. (at mile 1.0 east limits), which have since been removed.
The current signaling only allows for 30mph at these new turnouts, but also the entire Eastern corridor is speed restricted to 30mph anyways (starting from mile 1.7, were the line crosses over the Don river). Both those aspects will have to be modified before any speed increase occurs. The intent is to upgrade it to 60mph between 1.7 and 0.6 once the signal system is upgraded, though there may be a problem with the degree of curvature at mile 1.2. Though even if they have to reconstruct the track there I’m sure they will to accommodated the increase.
Currently it takes almost 3 minutes to cross this area, the speed increase will cut that almost in half. It may not seem like much but it'll make a huge difference in terms of reducing congestion and accommodating more trains in this section of track.
However the final approach to Union (eastern limits mile 0.6 to 0.0), the area where they have been working on over the past couple of weekends, will always only be 15mph as there is simply not enough space to accommodate longer/higher speed turnouts . The tracks are being reconfigured and decade old switches are being replaced to accommodate the new electronic signal/switching system.
The current system is manually operated from 3 different control towers. An operator has to pull a small lever/handle to cause a switch to move, in a room that has dozens of these little handles sticking out of a large machine. The operators are pretty quick with using this machine to line trains through the area. But as the number of trains increases, coordinating train movements in this way will become less and less efficient. The new system will no doubt be completely computerized and be operated from one location to coordinate all movements.
Also we have recently been further speed restricted to 10mph inside the train depot itself. Apparently there was some structure integrity concerns as heavy vibrations were noted in some tunnels underneath the shed while trains were passing above at 15mph. This is why the arrival time for the hourly was moved back by 1 minute - from 37 to 38 going west and 07 to 08 going east, past the hour. Hopefully the necessary repairs are made and this speed restriction is lifted. It only adds 45 seconds but again it makes a big difference capacity wise.