The blocks ingame are only updated and calculated in a specific range (around 200 blocks). Exact info here: (http://www.minecraftwiki.net/wiki/Chunk).
I started multiple minecarts on the 270 blockwide test track and same with the repeaters. When i stand at the beginning the blocks far away won't be updated. So the Redstone Signal "stops" and also minecarts have an undefined state. When i then fly to the end of the track i can see where the redstone stopped and also a minecart got stuck at the end but the other 2 i also sent away started travelling back when i went on my way to the end. The minecarts start all on the same block when the chunk gets loaded and do funny things then. Some get stuck some drive back and some proceed driving forward.
So the fix should be some kind of check when a chunk is loaded if there is some "connected" data in the previous chunk and then correctly work threw it. So minecarts proceed travelling in the correct direction and water goes 8 blocks and redstone updates as previous state.
I know the loading more chunks is a problem also like loading all redstone/mincart-tracks all the time. But for the redstone update it would be nice if these glitches get removed so when the chunk gets loaded the affected things still do what they should do!