I have noticed absolutely no difference moving water from an established tank to a new tank in aiding the cycle. As I understand it little to no bacteria is free floating. All you're doing for the most part is adding nitrates, which are of no benefit, to the new tank, and a miniscule amount of ammonia and nitrites which will only help if you already have a small amount of bacteria to feed, like in cycled biomedia.
I HAVE however, quick cycled tanks with established MEDIA, like ceramic rings, biowheels, etc.
It depends on how much of the media you use and how well cultured it is how long it takes for the new tank to completely cycle.
Mature nitrifying bacteria supposedly double in around 8 hours or more. So the less mature bacteria you start with the longer it's obviously going to take.
The amount of bacteria on an established tank is only enough as is needed to convert the amount of ammonia/nitrites in THAT tank. So if you take a little bit of media out of a tank it may or may not be enough to support the fish load you have in your own tank, and it may take awhile to gain enough bacteria to support that tank.
There's no such thing as instant cycling unless you're taking the exact amount of bacteria to support the fishload on your own tank, which is unlikely. You will always at least see a small rise in ammonia and nitrites over the course of a few days, and then they will drop in an amount of time dependant on how fast your bacteria are multiplying (temperature, pH, and other factors have an effect on this) and how much bacteria you started out with.
