That bag looks like the same proportions as the ones here in Ontario, but the volume is definitely different.

Here you can only buy 3 bags at a time. They come within a larger bag for a total volume of 4L. Each of the internal bags is either clear, white or translucent blue, with no branding or markings. Only the external bag contains the branding. The translucent blue and white are used by two brands of premium (filtered) milk.

Apart from that you can buy them in a carton in 1 and 2L sizes. You might still find it in 4L plastic jugs somewhere, but I haven't seen those in ages. Single-serve sizes are also available, but I'm talking about buying milk to put in your fridge for family.

Here's an example of a milk fridge in a supermarket:
http://nothingheavy.blogspot.com/2006/04/milk-bag.html

For commercial use, like offices, you can also buy it in Tetra packs as we had them at ATI. These were always from Parmalat. Tetra packed milk is the norm in Portugal (though I'm sure you can buy fresh in glass as well in some places). It doesn't have to be refrigerated until it's opened.