On Tuesday 4/14/15, MBTA Framingham / Worcester line train P508 (the express from Worcester at 7 AM) was cancelled. Reliable sources reveal that it was cancelled due to a lack of a conductor - but blame is being pointed at Keolis crew staffing for failing to send a conductor to staff the train. [All trains need a conductor and an engineer, and assistant conductors are not qualified to act as conductors.]
On Thursday 4/16/15, the same thing almost happened to P506 (the local from Worcester at 6:35 AM). Ty, the usual conductor for 506, was sick. Normal procedure is to utilize the 'extra board' - a standby collection of employees who can be sent to cover staff shortages. For whatever reason, instead of getting someone from the 'extra board,' Keolis utilized the 'house engineer' from Worcester to act as the conductor for 506. So instead of cancelling the train as they did with 508 on Tuesday (assuming someone from the 'extra board' was either unavailable or not available in sufficient time), 506 ran on a normal schedule with no delays.
The "house engineer" is an assignment at some terminal locations for an engineer to shuttle trains in and out of the yard, and assist with making up and breaking up trainsets. Sometimes referred to as a "herder job." So this person is not usually used to augment 'road crews.'
Hard to know what exactly happened, but my speculation is that the blowback from the cancelled 508 on Tuesday may have influenced Keolis to do a little out-of-the box thinking and use the "house engineer" for Thursday's 506. In my 10+ years riding the Fram / Wor, this is the first time I have seen the "house engineer" used as a conductor on a road job. Interesting.