Comparing the two tunnels is a bit unfair because the new construction is like digging 14 of the old tunnels.
The new tunnel is circle 60' in diameter, compared to the 30' semicircular train tunnel (8 times bigger), and the new tunnel is 1.75 miles long compared to one mile(.75x8=+6). Plus, the floor of the old tunnel was flat and only required laying train tracks. The new tunnel is circular and will require a double roadway and utility spaces.
If the new tunnel was dug with picks, shovels, and dynamite, it would take 14 times the 1.5 years of the old tunnel or 21 years total. Then start the construction of the interior infrastructure.
No, this isn't a project that would be feasible with picks and shovels.