From what I can gather, the bags are filled where their position is on the structure, instead of on the ground and then hoisted into place (a 30' long bag with dirt and cement in it must be pretty heavy no?)
I think that it would be quite easy to fill -- perhaps with an air compressor as aid? or a really long ramming rod / tamper type of deal.
I too was looking at calearth and it's homes -- pretty impressive, and goes along 'better' with my idea of green / sustainable construction. I love domes, but there is a lot of energy 'cost' associated with the production of the materials in their use (i.e. concrete, steel, perhaps foam, dunno).