>>1218094By the time the need for subways to NJ was evident, the subways were no longer private.
When the 7 line was recently extended(it used to end at the bus terminal) one of the options considered was extending into NJ instead of just to the railyards, but it involved a bureaucratic nightmare, as well as being way more expensive.
The current bus terminal was built with foundations for airrights development in mind, and there have been several proposals over the years for an office tower on top of it.