bricology, the whole point is to use it as a temporary shelter.
now, a functioning government can easily haul in dozens of loaded trucks from each available loading dock in just a few hours. i've seen 'em pack all of our containers, even in tight places such as this http://img89.imageshack.us/img89/9638/ac13agc1.jpg.
hell, i've seen an entire artillery battalion load up on very big trucks in just a few hours...

now, you mentioned that it'll be cheaper to build a "truly portable shelter". i'm intrigued. what IS a truly portable shelter? i've never seen a shelter that is big enough to house 4-6 people safely, yet small enough to be easily transported.

oh, and this is how one looks on the inside:
http://img144.imageshack.us/img144/1838/a010ajc4.jpg

As a soldier in the IDF, i lived in quite a few of those.
saying it's hard to transport is ridiculous! Containers are MEANT to be transported. all you need is a truck and a small crane.
As a private citizen it's hard to come by, but for government agencies this equipment is easily available en masse.

In Israel, most outposts are manned on rotation. every few months the occupying company takes all it's stuff and moves to another one (or to a training camp). that means that ALL of the equipment, from shirts and sleeping bags, to machine guns, is stored in shpping containers, and can be easily moved in a few hours.

now, i personally lived in containers, and i must say it's rather nice. the main problems are insulation and sound (it reverberates like hell!). but is sure as hell beats a tent!!!