When powering minecart booster / activator track, will not un-power previous tracks even if there's no direct power source near by.

Video: https://www.youtube.com/watch?v=MXS2yh1PAA0

To reproduce: have a line of booster tracks or activator tracks and keep powering the next one after.
by doing this you can power a mass amount of tracks without constant need for a redstone source