I had seen films of those monsters, but didn't know they were in use in Alberta. The films I saw I think were at coal mines.
I'm familar with the 20 something yard (wanna say 27) model that is used for most earthwork on construction jobs. The 40 yard models were the largest I remember being able to be moved in without extensive site assmbly.
The big ones like that, IIRC, take something like 40 or more haul trucks to get on site and then have to be assembled including welding the bed together.
Would have never guessed they moved 400 tons...