Update, 10:16 a.m.: The MBTA reports normal Red Line service has resumed.
A maintenance vehicle being used for some overnight work at Park Street derailed this morning, knocking out the third rail and completely disrupting the morning commute.
The T wrangled some buses to shuttle riders between Harvard and Broadway, but, of course, they proved unable to completely replace multi-car subway trains and riders from Cambridge to South Boston faced long waits just to get on a bus - at the start of what could be the hottest day of the year.
By 8:40 or so, T workers had managed to re-rail the thing so that they could drive it away from Park Street, in this photo forwarded by Tom Brand. He adds that once the vehicle cleared the Longfellow, it was driven off the tracks and onto the road, after T workers removed a portion of fence.