Yes, frrc, the P&W did clear their Gardner branch back in the Fall of '08, IIRC, for fully enclosed autoracks and high-cube/low-cube doublestacked container combos. I believe they funded this work with money provided by GATX's buy-in ownership stake.
The vast majority of money to support Davisville's rail-based auto/potential container traffic, also for fully enclosed autoracks and high-cube/low-cube container doublestack, has come from taxpayers, and, specifically U.S. taxpayers: $145 million from the Feds.; $51 million from RI; up to $5.5 million from MA; and, for the Bellows Falls tunnel potentially-related part of the project: $2 million from the Feds. and $ .7 million from VT. About $ 200 million all totalled.
Looks to me that they're doing about 30-40 carloads of inbound autos each week for distribution into New England...haven't seen evidence that they're loading outbound traffic at this point.
Can't see short-sea (by the seashore?) shipping offering much, if any, business potential since that simply represents a local distribution alternative to highway or rail from the larger ports of call, presumably NY/NJ or Halifax.