Once Evergreen Line opens, our "pan-shaped loop: will disappear and much of the M-Line confusion will also disappear.
See here for other loops on Metro systems (Bucharest and Newcastle look most like M-Line):
http://mic-ro.com/metro/metrorings.html
I like the event based names of the SkyTrain lines - it adds "local character" and ties to history.
To a visitor "Expo Line" would be no different than "A Line" or "ABC Line".
If you are appealing to visitors, you'd be trying to make things as generic as possible.
Is that a good thing (for the community)?
You may as well say that visitors won't know BC Place is a stadium, so lets call it BC Stadium.
But wait, where in BC is BC Stadium?
It should be Vancouver Stadium.
But wait, Vancouver has more than one stadium, too.
It should be Beatty Street Stadium, then all the visitors will know where it is.