Since joescanner is pretty busy...
MAX Light Rail currently (but will change I think next year) is on the
Portland Public Safety Radio System Trunking System, Portland, Multi-State - Scanner Frequencies system with police and lots of others, so try setting the bank to open/search mode and see if you can hear anything.
The control channel frequency I'm currently getting is 859.46250
Try these talk groups:
27824 Tri-Met (MAX) Rail Maintenance West
27856 Tri-Met (BUS) Operations Tac 3
27888 Tri-Met (ICS) Incident Command
27920 Tri-Met (BUS) Special Events
27952 Tri-Met (SAT) Customer Service
27984 Tri-Met (MAX) Rail Maintenance North
28016 Tri-Met (MAX) Tunnel
28048 Tri-Met (MAX) Rail Maintenance Tac 1
28080 Tri-Met (MAX) Fare Maintenance Tactical
28112 Tri-Met (FIO) Fare Inspection
28144 Tri-Met (MAX) Rail Maintenance East
28176 Tri-Met (MAX) Elmonica Rail Yard
28208 Tri-Met (MAX) Main 1 E.Light Rail Dispatch
28240 Tri-Met (MAX) Main 2 W. Light Rail Dispatch
28272 Tri-Met (MAX) Main 3 Administration
28304 Tri-Met (MAX) Ruby Junction Rail Yard
28336 Tri-Met (MAX) Rail Ch 6 (RL SUP/RL TAC 1)
28368 Tri-Met (MAX) Rail Ch 7 (RL TAC/RL TAC 2)
28400 Tri-Met (MAX) Rail Maintenance Tac 2
28432 Tri-Met (BUS) BUS Supervisors / Dispatch
28464 Tri-Met (SEC) Security BUST1
28496 Tri-Met (BUS) Operations Tac 2
28560 Tri-Met Announcement Talkgroup
38416 Streetcar Main
38448 Streetcar Tac 1
38480 Streetcar Tac 2