In Australia this method of construction is referred to as "waffle pod" - The name came from the fact that a finished slab would visually resemble a waffle from the underside - if you could see it.
The concept is based on living in a country where trades labour is expensive ( 3000 baht ish an hour ) and so commodity materials are cheap ( relative to trades labour ) so anything that can save time at the expense of low cost materials like polystyrene can represent a huge saving in construction costs - interestingly the exact opposite of building in asia.
The other benefits are that is really easy to calculate the exact quantity of concrete you will need as the footings are not dug in "variable" soil - ie the forms and pods provide exact measurements for the amount of concrete you need.
The finished slab is incredibly strong - stronger than regular slab construction, fast and where labour is expensive is much cheaper than regular construction ( a mute point in Thailand )
The pods are only there to support the concrete until it cures so in theory you can use any material, as long it can support the concrete - orginally pods where waxed paper boxes but they had trouble under the weight of men walking to pour the concrete and the concrete itself hence now they use polystrene pods.
I am building a house in thailand and am using this method of construction, couldn't find the pods here so I used the cheapest block I could find instead photo attached.
The only caution I would give you is that you mentioned "channels" every 2 - 4 Meters - that is incorrect, one the reasons that this construction method is stronger that a conventional raft slab is the channels are appx 1 m apart, there is reinforcing in between every pod. every 1M or so.
If I can give anyone here a piece of unsolicited advice about concrete it is this, buy yourself a concrete vibrator and give it you builder as a gift and insist he use it whenever pouring concreting, you can buy a small handheld vibrator for about 5000 baht, it will be the best 5000 baht you will ever spend.
Here is a link to a useful resource on waffle pods, lots of pics and other info.http://www.wafflepod.com/engineer/index.php