Add monorail tunneling capabilities

[Arikadesu]

Been looking for a mod for over an hour and come to realize the game simply does not support such an obvious desire. Please change monorail lines to allow below ground builds. There are times where I want to play around with mountainous maps and I'm unable to implement monorail lines as it would mean cutting through the mountains or having half the map as bridge systems which ruins the aesthetics I'm going for.

 

[Cityplanner 53]

For those who disagree, while actively going underground for a monorail wouldn't make sense, tunneling through a hill that's in the way may well do so.