The guys I watched install the 750MCM in a big computer room used the pipe trick John described. I had a piece of that 750 on my desk for years. I had never seen wire that big before.
I always wondered why they didn't use a parallel run of 250s but it wasn't my job.
That was a pretty tough "tug" too. I am not sure how far it was but it was from the basement below and not right under it.
They had two guys pushing and two guys pulling through a 4" pipe. (3 phases and an EGC) When I left they were talking about trying to find a come along.
I am still not sure they didn't open the pipe in the basement and pull it in two tugs then piecing it back together.