Since this appears to be the authoritative B&P tunnel thread, I guess I'll post this here.
The next round of public meetings regarding the B&P tunnel project will be held on June 16th, 2015. Meeting materials are available
here.
To me there is only one piece of semi-new information here. They have known for a while that they will need four tracks through Baltimore, and that much is not news. However, if you look at the "Track Requirements" page you will see that they are considering possibly building four new bored tunnels through Baltimore.
So the main takeaway is that they are considering three route alternatives - #2 (Update B&P tunnel), #3 (Great circle), #11 (Roberts Street South), and the four tracks (two pairs of tracks really) would be along one or two of those rotues. The possible combinations would be:
1. 2 tracks B&P + 2 tracks Great Circle
2. 2 tracks B&P + 2 tracks Roberts South
3. 4 tracks Great Circle
4. 4 tracks Roberts South
5. (Theoretically??) 2 tracks Great Circle, 2 tracks Roberts South.
Up until now I had assumed that there would be two new tunnels built and the B&P tunnels would be restored. That option is still on the table, but not a given. If they look at the 142 year old B&P tunnel and find it to be too inadequate (clearances, curvature, grades, ventilation, emergency egress, etc) or too far gone structurally, they might just abandon it.
I would think that an alternative reusing the B&P tunnel would probably be less expensive, but operationally inferior. I don't see much to recommend either the Great Circle or the Roberts South alignment over the other.