P508, the 7:00 AM inbound express from Worcester, operates on track 2 through this area. It is normal for the dispatcher to ask a train on a track next to a dead set to reduce speed for safety reasons as it passes by. It is NOT normal for the train on the opposite track to have to stop for 10 minutes.
However, at about 8:05 AM, P508 stopped adjacent to the broken down set and remained in Wellesley Square for about 10 minutes. Based on rider reports, I'm fairly confident I understand what happened.
To tie two trains together, a cable and a hose are needed to transmit both the compressed air for the braking system and the electrical and control signals for the locomotives and coaches. All train sets are supposed to have the hose and the "multiple-unit" (or "MU") cable on board in case they are needed. During previous break-downs, I have heard train crews looking for the cables and struggling to find them.
I suspect this is exactly what happened this morning. Neither P505 nor P507 had the cables or hoses on board, so P508 stopped to pass them the gear. A passenger observed cables being carried on the P508 side of the fence at Wellesley Square. There is no other reason for a crew member to be carrying cables on the TRACK 2 side of the fence.
It is a clear and direct screw-up by Keolis to allow 2 trainsets to depart Boston without MU cables. No excuse. At least 10 minutes of the delay for P508 can be attributed to this lack of following procedures. And it wasn't just one train that was missing the cables - but 2 trains!
I'm usually quick to defend Keolis when breakdowns happen - they didn't buy the old equipment, they are just trying to make under-invested infrastructure work. But the lack of MU cables on two trainsets is inexcusable. And I'm watching.
I asked @MBTA_CR to explain what happened and they did not provide an answer or response. If they provide a different story or explanation, I will immediately update this post with that info.