"Doesn't the New Brunswick Southern also have access to the port at St. John and connect with the MMA?"
NBS has no access to Halifax, only St John. In fact they switch most of CN's customers there under an agreement and hand off the majority of traffic to CN which routes it up and over Maine to Montreal. St John was marginalized as a container port as far back as the CP days and only currently hosts one or two container shipping lines weekly as opposed to a larger number of break-bulk shipping lines calling the port weekly. With that being said, I don't know why St John fell behind Halifax or even Montreal for container traffic? St John was one of the busiest ports in the world during WWII and the robust years that followed , served by both CN and CP, however was transformed into a large forest products, break-bulk and oil terminal by the Irving's but the container traffic slipped away. Even when CP owned the Moosehead and it was a single-line haul, St John's container traffic was only sporadic at best, overflowing when the St Lawrence Seaway was frozen, a trickle in the summer. While this makes St John a second tier port, its a major player in bulk (pellets, pulp, potash, oil) shipments and major competition to ports in Maine.
What does this mean for the Moosehead? Uncertainty. With MNR serving Irving's forest products needs in NB, as well as GNP, MMA is left to ship any outbound paper from GNP over the Moosehead as well as whatever NBS gives them (less than a train a day) at Brownsville Jct. And with maybe a train a day each way and all those non revenue producing rugged miles, the Moosehead may meet its maker. Any GNP traffic can either be routed to CN at St Leonard or Pan Am at Mattawamkeag. Even if Cates Street can re-invent the forest industry in northern Maine with its new technology at its East Millinocket/Millinocket mills, this is a straight shot down to Searsport and it wouldn't surprise me if Irving wouldn't try to capture this traffic on the basis that very little infrastructure would be needed at St John as opposed to Searsport where they are starting from scratch.
I too would be interested to hear who was looking over the property as well.