It's possible, but not likely due to a very low FAR (Floor Area Ratio) of the site, which is only 2. This means that since the Lot is 654' x 329' = 215,166sf, then we can build 2x that total square footage on this parcel of land. Granted, additional parcels of land will be needed for a stadium's footprint, but the adjacent lots also have an FAR of 2. The building volume can be any combination so long as it maintains the required zoning setbacks and maximum height (I haven't looked these up), so if you make a large plaze on the south size then you can take that un-built square footage and go higher in other parts. The problem being that a garage takes a lot of space up since parking spots and access lanes have minimum widths so there's no cutting corners when packing a minimum number of cars. The other variable that I don't know how it applies is the actual field area - if this doesn't count as built space since it isn't enclosed, then that's a huge plus, but if it does count (building & zoning codes are sometime strange) then that too will eat away a big chunk of what we can do.
To address your skepticism of building over the rails...... we would be purchasing/leasing the air rights of those land plots, which essentially is taking the unused FAR from them (because hey, how much construction have they done with railroad tracks) and adding it to us while also building in the air above the tracks. This is a very standard practice for developers in NYC.