Yup, I get to 120 no problem. I'd probably get higher if I had more upgrades too.
I think it would be fun to have a "maxed resource" mode, that is a lot like endless mode (scored based on efficiency), but you aren't resource constrained on trains/tunnels at any point, and you have the max number of lines available.
Anyway, I love the game! I do find that the replayability goes down because of the upgrade cap in endless mode.