Some troubles in writing a plugin

I want to write small plugin, that cancel minecart's collisions.
I add vehicle's listener, and do some experiments.
First of all: minecart vs minecart is entity collision, but if a cancel this (setCanselled(true)), cancels only collision inertia (persistance maybe? ), but minecart's stops.
Second: when minecarts collides - there was collision with block, that is under rails.
How i can do for minecarts pass each other?

p.s.: sorry, sorry for my very bad english!