Interesting. The costs would make the Big Dig look like child's play. Until the politics of supporting the Northeast changes cannot seeing enough national support.
Now the proposal. Exactly how are the tunnel bores supposed to work? 2 for Amtrak and 2 for BXM Metro? FRA and FTA would never allow joint use. So, 2 Main tracks will not be enough for MARC and Amtrak by the time this project would be complete. The anticipated increase in both Amtrak and Marc traffic will have most of the Penn line 4 Main track BAL <> WASH by that time. Two Main tracks to the station are enough not enough. As well at a minimum facility would need at least 8 station tracks. Commuters would loose the West Baltimore MARC station. Complete by 2030? Really?
This problem of freight trains having to still use the old B&P Bore is not going away. The maintenance costs are high and will not change. One proposed Amtrak bore probably would need to be built in the future for freight.
Now what in the "IDEA" has merit.
The route would be at least 5 minutes quicker than the present route. Probably more like 12 - 15minutes for Amtrak and maybe 5 minutes for MARC. As many have posted it is eliminating the slow parts saves time. Again 4 Main track bores are needed for MARC and Amtrak. The closeness of Camden and the proposed station has merit if Marc has some kind of problem on either route.