First off, new coordinates: N 42° 20.696' W 071° 05.105'.
Second off, it sounds like the mark was where NorStar thought it might be. Much of the construction in the area seems to have been completed, and the mark is now easily accessible.
As NorStar mentioned, Norway Street no longer continues east of Mass Ave (although, interestingly enough, the Christian Science Monitor building retains the Norway Street address, although it no longer abuts it). Furthermore, St. Paul Street, which formerly curved around the front of the Church, is gone as well.
The mark, however, lives on, at the western end of the wall, as described. The wall only reaches a foot or so above the ground, and has a metal railing to prevent people from falling into the A/C and other stuff pit below. To get to the mark, you have to go across a grassy area (well, it was dirt at the time, but presumably it will be landscaped).
I will submit a report to the NGS.