[StudentStuff]

Looks like the subway constructed there was done using cut & cover tunnels, which is commonly done today, its only when you get below a certain depth or have preexisting structures that you'd use a tunnel boring machine.

For rail those tend to be fairly reliable, though most rail alignments buy two or three so they can bore from both ends, and have a spare in case it pulls a Bertha (Seattle's recent highway tunneling nightmare).

What is different today is how impacts are considered. Politically savvy communities are able to cause perfectly good rights of way with existing rail to not be used for light rail or commuter rail. Happened over in Bellevue, much to the detriment of the city and its surrounding towns. Microsoft ain't too happy about that one!