I expect the friction coefficient to be the same, as it is both steel that the wheels are running on and I think they use the same kind of paint for it. I do think the IBox is stiffer and therefore less vibration will occur which will increase the speed, call it a lower practical friction or so
At Mechanical Engineering I learned that it is much stiffer to have the cross supports go through the main support. The forces are then divided over two walls, with just one it might fold/buckle. I'm pretty sure the supports are thus going through, the ladder is of course less important than the...
It doesn't look like they are doing that. I also doubt if you could stick a footer to a plain concrete floor, does not sound very strong to me.
Anyway, nice that there's track on site, hopefully it goes vertical soon