I can’t find it anywhere, but it would be really helpful.
I think they aren’t even implemented.
Science lab computers may have that map data. Not sure though but that’s my best bet.
AFAIK those can be found on computers in the sewage stations, those below the ground.
Lab computers (the ones with turrets guarding them) let you grab about 9 overmap sectors centered on the one containing the lab.
The underground portion of the sewage treatment plants has a computer that lets you grab a map of all sewer lines for about the same range.
You may be able to find Fun Stuff (in places covered by the Advanced Guides) that lets you get a complete map of your overmap sector. Those tend to have Nifty Side Effects though.
Currently, there’s no way to get a map of subway stations or subway lines, though. Sorry about that. 
Thanks.