There are monorail trains running on my HSRP tracks. How can I get Hsrp trains to run on my HSRP tracks?
Also, I would like to know if it is possible to make GLR-in-avenue go through a tunnel.
You have monorail trains on your HSRP because they are actually the same network and there is no way for the game to tell the difference. So you can choose a HSRP train, but then you will get HSRP trains on your monorail. So search on the LEX or STEX for either HSRP automata or Monorail automata.
It is not possible for GLR-in-Avenue to go through a tunnel however you can create underpasses for GLR-in-avenue using the FLUPs (also part of the NAM)