Things happen for a reason. When NS worked the agreement with Pan AM and got more rights on the CP line between Binghamton and Albany, they had a purpose and, IMO, I don't think that the purpose was to compete with CSX on the Buffalo-Boston traffic using the Tier.
I think that another strategy drove those agreements -- probably one that meshes with their corridor strategies.
Now if someone can convince me that operating over the Tier is just as efficient in terms of cost and time as the CSX Water Level route in getting from Buffalo to Albany, I'll gladly change my opinion.
Poppyl