This is not a real issue because it is actually working as intended but it will be a problem when everyone starts using Minecart "Pipes" with Chest Minecarts.
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.
So i guess in future the server has to check for minecart-tracks and redstone wire connections that it can update the whole construct and not only a specific number of blocks. This will be very hard to solve i think because of performance problems but i hope Mojang Stars will do it.