What is the state of the track from the mainline to the Portsmouth yard?
I think an additional two Downeasters each way running to Portsmouth could be pretty successful. I would estimate the travel time to Boston being equivalent to Dover-to-Boston; about 1.5 hours. By car is about 1.25 hours... without traffic, that is! A monthly pass would likely be 299 as with Dover and Durham and everything north. You'd save $80/month on tolls. So $219. The drive is about 60 miles, or 120 per day, and at 20 MPG you're going through 6 gallons per day, or roughly $22.20 at today's prices. That's $444 per month on gas. $219 - $444 = -225. You save 225 per month, or 2700 per year.
The only question is how many people make the commute. I'm going to guess a fairly decent amount. The station could be on either side of the Maplewood Ave crossing:
http://www.google.com/maps?ll=43.078265 ... 1&t=h&z=18
A layover could be tacked onto the yard.
I haven't seen this posted before, so sorry if this is a beaten horse.