I think that people over-complicate interlining....
If you were to use Moscow's or London's metro, of course you would be looking at the metro map to track where you are going, but you would pay more attention to where the train's final destination is so that you can verify if you're on the right train or not.
The colourful lines on the metro map really make no difference; it just makes it easier to figure out where you're going. Of course if there's a problem on the interlined tracks, it will effect more than one line but that would be the same case if that interlined portion was just a split line. So I really don't see the argument there

. And it's not like there needs to be a huge revamp of the software system to send a train to a different destination.
I just find it to be a huge inconvenience that for the commuter who leaves from Nanaimo or downtown to travel to Lake City Way Station (or something like that) is now forced to transfer trains (either at Commercial or Production Way) because of the updated system. I would rather have the Millennium line split than the expo line so that there are far less transfers for commuters.