Interesting. I thought this plan was nixed. Any ETA on this?
I think it withered on the vine and was forgotten about by anyone with the power to make it happen. Aside from money, there were some serious logistical challenges on the other side of the channel and questions about how to tie the line into the rest of the system in a way that wouldn't break things.
Regardless, it would be preferable if room was left to build a platform at some later date. Rails can be reconfigured. Building foundations... not so much.
With the way things are going in the Seaport, I'm not sure if that rail line will ever be used for freight.