I had three stations in a twisting loop. My guests refused to take the shuttle into the park ( even though it was free ).
I have a suspicion it might be because the distance wasn't great enough for their pathing to trigger an event ( e.g.: "useMonorail": Yes ). The event didn't instruct them to take the monorail, so the ride was an optional one as opposed to a mandatory one. See update below.
I'll investigate.
With regards to actual shuttling ( two stations, no loop ); it's a pity we can't do that.
------ UPDATE ------
Test 1:
Placed two stations at either end of the park.
Placed a ride attraction at the far end of park.
Result: Success, guests used the monorail.
Test 2:
Placed two stations at either end of the park.
No ride attraction.
Result: Failed, guests did not use the monorail.
Test 3:
Placed two stations at either end of the park. $1 per ride.
Placed a ride attraction at the far end of park.
Result: Success, guests used the monorail.
Test 4:
Placed two stations close together. One above ground, one below. Free ride.
Placed two ride attractions.
Result: Success, guests used the monorail.
( I didn't set my path properly so Test 4 was a failure. After fixing the path, it works. )
Conclusion: Guests *will* use the Monorail track as long as there is an attraction to lure them into the park.
------ END OF UPDATE ------
Wait...What you can't do is a shuttling monorail. You have to do a loop.
I created a monorail station near the park entrance that did a loop into the back of the park and put a second station there and continued back to the first (so I had two stations and a big loop).
At first I had a path connecting the front of the park to the back but as an experiment, I removed the path and all the people coming into the park would go straight to the front monorail and ride. Those that were already in the park that wanted to leave would go to the back station and ride back to leave. It worked perfectly. The game even allowed those without enough money to get on the back station so no one got stuck. It worked perfectly.
Is this what you were asking about or was it a shuttling (back and forth) train/monorail?